2,688 research outputs found
A new construction of perfectly matched layers for the linearized Euler equations
Based on a PML for the advective wave equation, we propose two PML models for
the linearized Euler equations. The derivation of the first model can be
applied to other physical models. The second model was implemented. Numerical
results are shown.Comment: submitted for publication on February 1st 2005 What's new: interface
conditions for the first PML model, a 3D section, more numerical result
Magnetic induction maps in a magnetized spherical Couette flow experiment
The DTS experiment is a spherical Couette flow experiment with an imposed
dipolar magnetic field. Liquid sodium is used as a working fluid. In a series
of measurement campaigns, we have obtained data on the mean axisymmetric
velocity, the mean induced magnetic field and electric potentials. All these
quantities are coupled through the induction equation. In particular, a strong
omega-eff ect is produced by di fferential rotation within the fluid shell,
inducing a significant azimuthal magnetic field. Taking advantage of the simple
spherical geometry of the experiment, I expand the azimuthal and meridional
fields into Legendre polynomials and derive the expressions that relate all
measurements to the radial functions of the velocity field for each harmonic
degree. For small magnetic Reynolds numbers Rm the relations are linear, and
the azimuthal and meridional equations decouple. Selecting a set of
measurements for a given rotation frequency of the inner sphere (Rm = 9.4), I
invert simultaneously the velocity and the magnetic data and thus reconstruct
both the azimuthal and the meridional fields within the fluid shell. The
results demonstrate the good internal consistency of the measurements, and
indicate that turbulent non-axisymmetric fluctuations do not contribute
significantly to the axisymmetric magnetic induction.Comment: soumis au Comptes Rendus Physiqu
Online Estimation of Battery Lifetime for Wireless Sensors Network
Battery is a major hardware component of wireless sensor networks. Most of
them have no power supply and are generally deployed for a long time.
Researches have been done on battery physical model and their adaptation for
sensors. We present an implementation on a real sensor operating system and how
architectural constraints have been assumed. Experiments have been made in
order to test the impact of some parameter, as the application throughput, on
the battery lifetime
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