54,339 research outputs found
BeppoSAX LECS background subtraction techniques
We present 3 methods for the subtraction of non-cosmic and unresolved cosmic
backgrounds observed by the Low-Energy Concentrator Spectrometer (LECS)
on-board BeppoSAX. Removal of these backgrounds allows a more accurate modeling
of the spectral data from point and small-scale extended sources. At high
(>|25| degree) galactic latitudes, subtraction using a standard background
spectrum works well. At low galactic latitudes, or in complex regions of the
X-ray sky, two alternative methods are presented. The first uses counts
obtained from two semi-annuli near the outside of the LECS field of view to
estimate the background at the source location. The second method uses ROSAT
Position Sensitive Proportional Counter (PSPC) all-sky survey data to estimate
the LECS background spectrum for a given pointing position. A comparison of the
results from these methods provides an estimate of the systematic
uncertainties. For high galactic latitude fields, all 3 methods give 3 sigma
confidence uncertainties of <0.9 10^-3 count/s (0.1-10 keV), or <1.5 10^-3
count/s (0.1-2 keV). These correspond to 0.1-2.0 keV fluxes of 0.7-1.8 and
0.5-1.1 10^-13 erg/cm2/s for a power-law spectrum with a photon index of 2 and
photoelectric absorption of 3 10^20 and 3 10^21 atom/cm2, respectively. At low
galactic latitudes, or in complex regions of the X-ray sky, the uncertainties
are a factor ~2.5 higher.Comment: 13 pages. Accepted for publication in A&A
Background subtraction based on Local Shape
We present a novel approach to background subtraction that is based on the
local shape of small image regions. In our approach, an image region centered
on a pixel is mod-eled using the local self-similarity descriptor. We aim at
obtaining a reliable change detection based on local shape change in an image
when foreground objects are moving. The method first builds a background model
and compares the local self-similarities between the background model and the
subsequent frames to distinguish background and foreground objects.
Post-processing is then used to refine the boundaries of moving objects.
Results show that this approach is promising as the foregrounds obtained are
com-plete, although they often include shadows.Comment: 4 pages, 5 figures, 3 tabl
Semantic Background Subtraction
peer reviewedWe introduce the notion of semantic background subtraction, a novel framework for motion detection in video sequences. The key innovation consists to leverage object-level semantics to address the variety of challenging scenarios for background subtraction. Our framework combines the information of a semantic segmentation algorithm, expressed by a probability for each pixel, with the output of any background subtraction algorithm to reduce false positive detections produced by illumination changes, dynamic backgrounds, strong shadows, and ghosts. In addition, it maintains a fully semantic background model to improve the detection of camouflaged foreground objects. Experiments led on the CDNet dataset show that we managed to improve, significantly, almost all background subtraction algorithms of the CDNet leaderboard, and reduce the mean overall error rate of all the 34 algorithms (resp. of the best 5 algorithms) by roughly 50% (resp. 20%). Note that a C++ implementation of the framework is available at http://www.telecom.ulg.ac.be/semantic
Medium Recoils and background subtraction in JEWEL
\textsc{Jewel} is a fully dynamical event generator for jet evolution in a
dense QCD medium, which has been validated for multiple jet and jet-like
observables. Jet constituents (partons) undergo collisions with thermal partons
from the medium, leading to both elastic and radiative energy loss. The
recoiling medium scattering centers carry away energy and momentum from the
jet. Keeping track of these recoils is essential for the description of
intra-jet observables. Since the thermal component of the recoils is part of
the soft background activity, comparison with data on jet observables requires
the implementation of a background subtraction procedure. We will show two
independent procedures through which background subtraction can be performed
and discuss the impact of the medium recoil on jet shape observables and
jet-background correlations. Keeping track of the medium recoil significantly
improves the \textsc{Jewel} description of jet shape measurements.Comment: Proceedings for talk given at HP 2016 at Wuhan Chin
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