17,480 research outputs found
A Fusion Framework for Camouflaged Moving Foreground Detection in the Wavelet Domain
Detecting camouflaged moving foreground objects has been known to be
difficult due to the similarity between the foreground objects and the
background. Conventional methods cannot distinguish the foreground from
background due to the small differences between them and thus suffer from
under-detection of the camouflaged foreground objects. In this paper, we
present a fusion framework to address this problem in the wavelet domain. We
first show that the small differences in the image domain can be highlighted in
certain wavelet bands. Then the likelihood of each wavelet coefficient being
foreground is estimated by formulating foreground and background models for
each wavelet band. The proposed framework effectively aggregates the
likelihoods from different wavelet bands based on the characteristics of the
wavelet transform. Experimental results demonstrated that the proposed method
significantly outperformed existing methods in detecting camouflaged foreground
objects. Specifically, the average F-measure for the proposed algorithm was
0.87, compared to 0.71 to 0.8 for the other state-of-the-art methods.Comment: 13 pages, accepted by IEEE TI
Star formation in a diffuse high-altitude cloud?
A recent discovery of two stellar clusters associated with the diffuse
high-latitude cloud HRK 81.4-77.8 has important implications for star formation
in the Galactic halo. We derive a plausible distance estimate to HRK 81.4-77.8
primarily from its gaseous properties. We spatially correlate state-of-the-art
HI, far-infrared and soft X-ray data to analyze the diffuse gas in the cloud.
The absorption of the soft X-ray emission from the Galactic halo by HRK
81.4-77.8 is used to constrain the distance to the cloud. HRK 81.4-77.8 is most
likely located at an altitude of about 400 pc within the disk-halo interface of
the Milky Way Galaxy. The HI data discloses a disbalance in density and
pressure between the warm and cold gaseous phases. Apparently, the cold gas is
compressed by the warm medium. This disbalance might trigger the formation of
molecular gas high above the Galactic plane on pc to sub-pc scales.Comment: 6 pages, 4 figures, accepted for publication in Astronomy &
Astrophysic
Finite Element Analysis of Electromagnetic Waves in Two-Dimensional Transformed Bianisotropic Media
We analyse wave propagation in two-dimensional bianisotropic media with the
Finite Element Method (FEM). We start from the Maxwell-Tellegen's equations in
bianisotropic media, and derive some system of coupled Partial Difference
Equations (PDEs) for longitudinal electric and magnetic field components.
Perfectly Matched Layers (PMLs) are discussed to model such unbounded media. We
implement these PDEs and PMLs in a finite element software. We apply
transformation optics in order to design some bianisotropic media with
interesting functionalities, such as cloaks, concentrators and rotators. We
propose a design of metamaterial with concentric layers made of homogeneous
media with isotropic permittivity, permeability and magneto-electric parameters
that mimic the required effective anisotropic tensors of a bianisotropic cloak
in the long wavelength limit (homogenization approach). Our numerical results
show that well-known metamaterials can be transposed to bianisotropic media.Comment: 26 pages, 8 figure
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