25,443 research outputs found
Accurate Estimation of a Coil Magnetic Dipole Moment
In this paper, a technique for accurate estimation of the moment of magnetic
dipole is proposed. The achievable accuracy is investigated, as a function of
measurement noise affecting estimation of magnetic field cartesian components.
The proposed technique is validated both via simulations and experimentally.Comment: Preprin
Magnetocatalytic Adiabatic Spin Torque Orbital Transformations for Novel Chemical and Catalytic Reaction Dynamics: The Little Effect
In this manuscript the theory and phenomena associated with the Little Effect
are introduced as the spin induced orbital dynamics of confined fermions under
strong magnetic and thermal environments. This Little Effect is considered in
details for the electron transfer reactions associated with redox processes of
Cu-Ag alloy within deionized water and for the orbital dynamics during the iron
catalyzed covalent bond rearrangements associated with amorphous carbon
conversion to diamond. Furthermore, prolong extreme conditions of 74,000 amps,
403 V, strong Lorentz compression, and thermal stresses upon this Cu-Ag- H2O
system on the basis of the Little Effect of high spin, thermally induced
orbital dynamics are predicted and demonstrated to cause the magnetically
organized reverse beta, electron capture, proton capture and neutron capture
processes for various infrequent pycnonuclear transmutations within the Cu-Ag
coil. The general experimental verification and the broad implications of this
Little Effect on chemistry are demonstrated within these two ideal systems: an
ionic case and a molecular case. The Little Effect is contrasted with the
Hedvall Effect as a dynamical phenomenon causing the kinematics of the Hedvall
Effect. The compatibility of the Little Effect with the Woodward-Hoffmann Rule
is demonstrated. The Little Effect provides greater understanding of order in
systems far from equilibrium. The implications of the Little Effect for other
interesting phenomena such as ferromagnetism, unconventional magnetism,
superparamagnetism, superconductivity, and pycnonuclear effects are concluded
Practical Accuracy Limits of Radiation-Aware Magneto-Inductive 3D Localization
The key motivation for the low-frequency magnetic localization approach is
that magnetic near-fields are well predictable by a free-space model, which
should enable accurate localization. Yet, limited accuracy has been reported
for practical systems and it is unclear whether the inaccuracies are caused by
field distortion due to nearby conductors, unconsidered radiative propagation,
or measurement noise. Hence, we investigate the practical performance limits by
means of a calibrated magnetoinductive system which localizes an active
single-coil agent with arbitrary orientation, using 4 mW transmit power at 500
kHz. The system uses eight single-coil anchors around a 3m x 3m area in an
office room. We base the location estimation on a complex baseband model which
comprises both reactive and radiative propagation. The link coefficients, which
serve as input data for location estimation, are measured with a multiport
network analyzer while the agent is moved with a positioner device. This
establishes a reliable ground truth for calibration and evaluation. The system
achieves a median position error of 3.2 cm and a 90th percentile of 8.3 cm.
After investigating the model error we conjecture that field distortion due to
conducting building structures is the main cause of the performance bottleneck.
The results are complemented with predictions on the achievable accuracy in
more suitable circumstances using the Cram\'er-Rao lower bound.Comment: To appear at the IEEE ICC 2019 Workshops. This work has been
submitted to the IEEE for possible publication. Copyright may be transferred
without notice, after which this version may no longer be accessibl
Experimental demonstration of a mu=-1 metamaterial lens for magnetic resonance imaging
In this work a mu=-1 metamaterial (MM) lens for magnetic resonance imaging
(MRI) is demonstrated. MRI uses surface coils to detect the radiofrequency(RF)
energy absorbed and emitted by the nuclear spins in the imaged object. The
proposed MM lens manipulates the RF field detected by these surface coils, so
that the coil sensitivity and spatial localization is substantially improved.
Beyond this specific application, we feel that the reported results are the
experimental confirmation of a new concept for the manipulation of RF field in
MRI, which paves the way to many other interesting applications.Comment: 9 pages, 3 figure
Control of stochasticity in magnetic field lines
We present a method of control which is able to create barriers to magnetic
field line diffusion by a small modification of the magnetic perturbation. This
method of control is based on a localized control of chaos in Hamiltonian
systems. The aim is to modify the perturbation locally by a small control term
which creates invariant tori acting as barriers to diffusion for Hamiltonian
systems with two degrees of freedom. The location of the invariant torus is
enforced in the vicinity of the chosen target. Given the importance of
confinement in magnetic fusion devices, the method is applied to two examples
with a loss of magnetic confinement. In the case of locked tearing modes, an
invariant torus can be restored that aims at showing the current quench and
therefore the generation of runaway electrons. In the second case, the method
is applied to the control of stochastic boundaries allowing one to define a
transport barrier within the stochastic boundary and therefore to monitor the
volume of closed field lines
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