41 research outputs found
Second-harmonic generation from coupled plasmon modes in a single dimer of gold nanospheres
We show that a dimer made of two gold nanospheres exhibits a remarkable
efficiency for second-harmonic generation under femtosecond optical excitation.
The detectable nonlinear emission for the given particle size and excitation
wavelength arises when the two nanoparticles are as close as possible to
contact, as in situ controlled and measured using the tip of an atomic force
microscope. The excitation wavelength dependence of the second-harmonic signal
supports a coupled plasmon resonance origin with radiation from the dimer gap.
This nanometer-size light source might be used for high-resolution near-field
optical microscopy.Comment: 6 pages, 5 figure
Wide frequency range analysis of the electromagnetic emissions of electrical machine for diagnosis
The paper presents the possibilities to evaluate the health of an electrical
machine by analyzing its electromagnetic emissions. Different piece of
information can be detected according to the frequency range. First of all,
a monitoring system sensitive to the degradation of the turn-to-turn
insulation quality of the stator winding is presented; it is based on high
frequency electromagnetic emissions. The second part of the paper is based
on the medium and low frequency emission analysis. It explains how to detect
turn-to-turn short circuits in stator windings or in the excitation coils of
synchronous machines
Influence of a charging current with a sinusoidal perturbation on the performance of a lead-acid battery
International audienc
Analytical computation of an AC machine external magnetic field
This paper presents an analytical approach to
estimate the magnitude of a flux density component at a point located
outside an AC machine. The study uses the concept of attenuation
coefficients which are determined using several hypotheses. The developments
consider the different media according to they are flowed by eddy currents
or not. Then, the calculations are performed in each medium
Induction machine fault diagnosis using an external radial flux sensor
This paper presents a method for detecting faults in the induction machine
using a flux sensor which measures the external radial leakage magnetic
field of the machine. The procedure uses the spectral lines that correspond
to the slotting effect which causes harmonics in the machine air gap. These
harmonic frequencies, which are about a few kHz occur in a part of the
spectra which is not very dense compared to the one that corresponds to the
low frequencies due to the supply or the rotor revolution speed. The
considered components can also be detected in the radial magnetic field
flowing out of the machine. It can be shown that specific faults lead to
additional spectral lines which appear clearly near the original ones due to
the slotting effect. Two faults, which can be detected with the same
magnetic flux sensor, are presented in this paper: the first one
corresponds to a broken rotor bar, the second one is a stator inter turn
short circuit
Conception of a wireless cell for the energy consumption diagnosis of AC rotating machines
International audienc