4,958 research outputs found
Edge Potential Functions (EPF) and Genetic Algorithms (GA) for Edge-Based Matching of Visual Objects
Edges are known to be a semantically rich representation of the contents of a digital image. Nevertheless, their use in practical applications is sometimes limited by computation and complexity constraints. In this paper, a new approach is presented that addresses the problem of matching visual objects in digital images by combining the concept of Edge Potential Functions (EPF) with a powerful matching tool based on Genetic Algorithms (GA). EPFs can be easily calculated starting from an edge map and provide a kind of attractive pattern for a matching contour, which is conveniently exploited by GAs. Several tests were performed in the framework of different image matching applications. The results achieved clearly outline the potential of the proposed method as compared to state of the art methodologies. (c) 2007 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other users, including reprinting/ republishing this material for advertising or promotional purposes, creating new collective works for resale or redistribution to servers or lists, or reuse of any copyrighted components of this work in other works
Optimization in Differentiable Manifolds in Order to Determine the Method of Construction of Prehistoric Wall-Paintings
In this paper a general methodology is introduced for the determination of
potential prototype curves used for the drawing of prehistoric wall-paintings.
The approach includes a) preprocessing of the wall-paintings contours to
properly partition them, according to their curvature, b) choice of prototype
curves families, c) analysis and optimization in 4-manifold for a first
estimation of the form of these prototypes, d) clustering of the contour parts
and the prototypes, to determine a minimal number of potential guides, e)
further optimization in 4-manifold, applied to each cluster separately, in
order to determine the exact functional form of the potential guides, together
with the corresponding drawn contour parts. The introduced methodology
simultaneously deals with two problems: a) the arbitrariness in data-points
orientation and b) the determination of one proper form for a prototype curve
that optimally fits the corresponding contour data. Arbitrariness in
orientation has been dealt with a novel curvature based error, while the proper
forms of curve prototypes have been exhaustively determined by embedding
curvature deformations of the prototypes into 4-manifolds. Application of this
methodology to celebrated wall-paintings excavated at Tyrins, Greece and the
Greek island of Thera, manifests it is highly probable that these
wall-paintings had been drawn by means of geometric guides that correspond to
linear spirals and hyperbolae. These geometric forms fit the drawings' lines
with an exceptionally low average error, less than 0.39mm. Hence, the approach
suggests the existence of accurate realizations of complicated geometric
entities, more than 1000 years before their axiomatic formulation in Classical
Ages
Automated Bedform Identification—A Meta-Analysis of Current Methods and the Heterogeneity of Their Outputs
Ongoing efforts to characterize underwater dunes have led to a considerable number of freely available tools that identify these bedforms in a (semi-)automated way. However, these tools differ with regard to their research focus and appear to produce results that are far from unequivocal. We scrutinize this assumption by comparing the results of five recently published dune identification tools in a comprehensive meta-analysis. Specifically, we analyze dune populations identified in three bathymetries under diverse flow conditions and compare the resulting dune characteristics in a quantitative manner. Besides the impact of underlying definitions, it is shown that the main heterogeneity arises from the consideration of a secondary dune scale, which has a significant influence on statistical distributions. Based on the quantitative results, we discuss the individual strengths and limitations of each algorithm, with the aim of outlining adequate fields of application. However, the concerted bedform analysis and subsequent combination of results have another benefit: the creation of a benchmarking data set which is inherently less biased by individual focus and therefore a valuable instrument for future validations. Nevertheless, it is apparent that the available tools are still very specific and that end-users would profit by their merging into a universal and modular toolbox
A Search for the Most Massive Galaxies. II. Structure, Environment and Formation
We study a sample of 43 early-type galaxies, selected from the SDSS because
they appeared to have velocity dispersion > 350 km/s. High-resolution
photometry in the SDSS i passband using HRC-ACS on board the HST shows that
just less than half of the sample is made up of superpositions of two or three
galaxies, so the reported velocity dispersion is incorrect. The other half of
the sample is made up of single objects with genuinely large velocity
dispersions. None of these objects has sigma larger than 426 +- 30 km/s. These
objects define rather different relations than the bulk of the early-type
galaxy population: for their luminosities, they are the smallest, most massive
and densest galaxies in the Universe. Although the slopes of the scaling
relations they define are rather different from those of the bulk of the
population, they lie approximately parallel to those of the bulk "at fixed
sigma". These objects appear to be of two distinct types: the less luminous
(M_r>-23) objects are rather flattened and extremely dense for their
luminosities -- their properties suggest some amount of rotational support and
merger histories with abnormally large amounts of gaseous dissipation. The more
luminous objects (M_r<-23) tend to be round and to lie in or at the centers of
clusters. Their properties are consistent with the hypothesis that they are
BCGs. Models in which BCGs form from predominantly radial mergers having little
angular momentum predict that they should be prolate. If viewed along the major
axis, such objects would appear to have abnormally large sigma for their sizes,
and to be abnormally round for their luminosities. This is true of the objects
in our sample once we account for the fact that the most luminous galaxies
(M_r<-23.5), and BCGs, become slightly less round with increasing luminosity.Comment: 21 pages, 19 figures, accepted for publication in MNRA
2FGL J0846.0+2820: A new neutron star binary with a giant secondary and variable -ray emission
We present optical photometric and spectroscopic observations of the likely
stellar counterpart to the unassociated \emph{Fermi}-Large Area Telescope (LAT)
-ray source 2FGL J0846.0+2820, selected for study based on positional
coincidences of optical variables with unassociated LAT sources. Using optical
spectroscopy from the SOAR telescope, we have identified a late-G giant in an
eccentric ( = 0.06) 8.133 day orbit with an invisible primary. Modeling the
spectroscopy and photometry together lead us to infer a heavy neutron star
primary of and a partially stripped giant secondary of . H emission is observed in some of the spectra, perhaps
consistent with the presence of a faint accretion disk. We find the
-ray flux of 2FGL J0846.0+2820 dropped substantially in mid-2009,
accompanied by an increased variation in the optical brightness, and since then
it has not been detected by \emph{Fermi}. The long period and giant secondary
are reminiscent of the -ray bright binary 1FGL J1417.7--4407, which
hosts a millisecond pulsar apparently in the final stages of the pulsar
recycling process. The discovery of 2FGL J0846.0+2820 suggests the
identification of a new subclass of millisecond pulsar binaries that are the
likely progenitors of typical field millisecond pulsars.Comment: 12 pages, 8 figures, 3 tables. Accepted for publication in Ap
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