241 research outputs found
Inverse scattering for vowel articulation with frequency-domain data
An inverse scattering problem is analyzed for vowel articulation in the human
vocal tract. When a unit amplitude, monochromatic, sinusoidal volume velocity
is sent from the glottis towards the lips, various types of scattering data are
used to examine whether the cross sectional area of the vocal tract can
uniquely be determined by each data set. Among the data sets considered are the
absolute value of the pressure measured at a microphone placed at some distance
from the lips, the pressure at the lips, and the transfer function from the
glottis to the lips. In case of nonuniqueness, it is indicated what additional
information may be used for the unique determination.Comment: 29 pages, 9 figure
Retrieval of depth profile of nano scale thin films by one directional polarization analysis in neutron specular reflectometry
Recently it has been shown that the modules and phase of complex reflection
coefficient can be determined by using a magnetic substrate and polarized
neutrons. Several other methods have also been worked out based on measurement
of polarizations of reflected neutrons from magnetic reference layers and
magnetic substrate. However, due to the fact that available reflectometers are
limited in the choice of polarization of reflected beam in the same direction
as the polarization of the incident beam, neither of the methods which are
based on polarization analysis, has been proven to be experimentally practical.
In this paper, we have proposed a new method for determining the phase of
reflection coefficient which is based on two measurements of polarization which
correspond to two magnetic fields with the same magnitudes and different
orientations. The polarization analysis is performed in the same direction as
the polarization of the incident beam and is well suited for available
reflectometers. The problems envisaged in implementation of the method are also
discussed.Comment: 5 pages, 6 figure
Inverse scattering on the line for a generalized nonlinear Schroedinger equation
A one-dimensional generalized nonlinear Schroedinger equation is considered,
and the corresponding inverse scattering problem is analyzed when the potential
is compactly supported and depends on the wave function. The unique recovery of
the potential is established from an appropriate set of scattering data.Comment: 20 page
Identification of hydrodynamic forces developed by flapping fins in a watercraft propulsion flow field
In this work, the data analysis of oscillating flapping fins is conducted for mathematical model. Data points of heave and surge force obtained by the CFD (Computational Fluid Dynamics) for different geometrical kinds of flapping fins. The fin undergoes a combination of vertical and angular oscillatory motion, while travelling at constant forward speed. The surge thrust and heave lift are generated by the combined motion of the flapping fins, especially due to the carrier vehicle’s heave and pitch motion will be investigated to acquire system identification with CFD data available while the fin pitching motion is selected as a function of fin vertical motion and it is imposed by an external mechanism. The data series applied to model unsteady lifting flow around the system will be employed to develop an optimization algorithm to establish an approximation transfer function model for heave force and obtain a predicting black box system with nonlinear theory for surge force with fin motion control synthesis
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