5,301 research outputs found
WAVELET BASED NONLINEAR SEPARATION OF IMAGES
This work addresses a real-life problem corresponding
to the separation of the nonlinear mixture of images which
arises when we scan a paper document and the image from
the back page shows through.
The proposed solution consists of a non-iterative procedure
that is based on two simple observations: (1) the high
frequency content of images is sparse, and (2) the image
printed on each side of the paper appears more strongly in
the mixture acquired from that side than in the mixture acquired from the opposite side.
These ideas had already been used in the context of nonlinear denoising source separation (DSS). However, in that method the degree of separation achieved by applying these ideas was relatively weak, and the separation had to be improved by iterating within the DSS scheme. In this paper the application of these ideas is improved by changing the competition function and the wavelet transform that is used. These improvements allow us to achieve a good separation in one shot, without the need to integrate the process into an iterative DSS scheme. The resulting separation process is both nonlinear and non-local.
We present experimental results that show that the method
achieves a good separation quality
A logic for n-dimensional hierarchical refinement
Hierarchical transition systems provide a popular mathematical structure to
represent state-based software applications in which different layers of
abstraction are represented by inter-related state machines. The decomposition
of high level states into inner sub-states, and of their transitions into inner
sub-transitions is common refinement procedure adopted in a number of
specification formalisms.
This paper introduces a hybrid modal logic for k-layered transition systems,
its first-order standard translation, a notion of bisimulation, and a modal
invariance result. Layered and hierarchical notions of refinement are also
discussed in this setting.Comment: In Proceedings Refine'15, arXiv:1606.0134
Schwarzschild-like black holes: Light-like trajectories and massless scalar absorption
Black holes are among the most intriguing objects in nature. They are
believed to be fully described by General Relativity (GR), and the
astrophysical black holes are expected to belong to the Kerr family, obeying
the no-hair theorems. Alternative theories of gravity or parameterized
deviations of GR allow black hole solutions, which have additional parameters
other than mass and angular momentum. We analyze a Schwarzschild-like metric,
proposed by Johannsen and Psaltis, characterized by its mass and a deformation
parameter. We compute the absorption cross section of massless scalar waves for
different values of this deformation parameter and compare it with the
corresponding scalar absorption cross section of the Schwarzschild black hole.
We also present analytical approximations for the absorption cross section in
the high-frequency regime. We check the consistence of our results comparing
the numerical and analytical approaches, finding excellent agreement.Comment: 8 pages, 14 figure
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