5,820 research outputs found
Nuclear stopping and sideward-flow correlation from 0.35A to 200A GeV
The correlation between the nuclear stopping and the scale invariant nucleon
sideward flow at energies ranging from those available at the GSI heavy ion
synchrotron (SIS) to those at the CERN Super Proton Synchrotron (SPS) is
studied within ultrarelativistic quantum molecular dynamics (UrQMD). The
universal behavior of the two experimental observables for various colliding
systems and scale impact parameters are found to be highly correlated with each
other. As there is no phase transition mechanism involved in the UrQMD, the
correlation may be broken down by the sudden change of the bulk properties of
the nuclear matter, such as the formation of quark-gluon plasma (QGP), which
can be employed as a QGP phase transition signal in high-energy heavy ion
collisions. Furthermore, we also point out that the appearance of a breakdown
of the correlation may be a powerful tool for searching for the critical point
on the QCD phase diagram.Comment: 5 pages, 4 figure
The spectral radius of minor free graphs
In this paper, we present a sharp upper bound for the spectral radius of an
-vertex graph without -minor for sufficient large , where is
obtained from the complete graph by deleting disjointed paths.
Furthermore, the graphs which achieved the sharp bound are characterized. This
result may be regarded to be an extended revision of the number of edges in an
-vertex graph without -minor.Comment: 18 pages, 1 figur
The signless Laplacian spectral radius of graphs without trees
Let be the signless Laplacian matrix of a simple graph of
order , where and are the degree diagonal matrix and the
adjacency matrix of , respectively. In this paper, we present a sharp upper
bound for the signless spectral radius of without any tree and characterize
all extremal graphs which attain the upper bound, which may be regarded as a
spectral extremal version for the famous Erd\H{o}s-S\'{o}s conjecture.Comment: 12 page
Localizing Region-Based Level-set Contouring for Common Carotid Artery in Ultrasonography
 This work developed a fully-automated and efficient method for detecting contour of common carotid artery in the cross section view of two-dimensional B-mode sonography. First, we applied a preprocessing filter to the ultrasound image for the sake of reducing speckle. An adaptive initial contouring method was then performed to obtain the initial contour for level set segmentation. Finally, the localizing region-based level set segmentation automatically extracted the precise contours of common carotid artery. The proposed method evaluated 130 ultrasound images from three healthy volunteers and the segmentation results were compared to the boundaries outlined by an expert. Preliminary results showed that the method described here could identify the contour of common carotid artery with satisfactory accuracy in this dataset
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