62,042 research outputs found
QCD Sum Rule for S_{11}(1535)
We propose a new interpolating field for S(1535) to determine its mass
from QCD sum rules. In the nonrelativistic limit, this interpolating field
dominantly reduces to two quarks in the s-wave state and one quark in the
p-wave state. An optimization procedure, which makes use of a duality relation,
yields the interpolating field which overlaps strongly with the negative-parity
baryon and at the same time does not couple at all to the low lying
positive-parity baryon. Using this interpolating field and applying the
conventional QCD sum rule analysis, we find that the mass of S is
reasonably close to the experimentally known value, even though the precise
determination depends on the poorly known quark-gluon condensate. Hence our
interpolating field can be used to investigate the spectral properties of
S(1535).Comment: 12 pages, Revtex, 1 ps figure available from author
symmetry restoration in QCD with flavors
Recently, there have been reports that the chirally restored phase of QCD is
effectively symmetric under rather than . We supplement their argument by including the contributions from
topologically nontrivial gauge field configurations and discuss how the
conclusions are modified. General statements are made concerning the particle
spectrum of QCD with light flavors in the high temperature chirally
restored phase.Comment: 6 pages, no figures, revte
Visual-hint Boundary to Segment Algorithm for Image Segmentation
Image segmentation has been a very active research topic in image analysis
area. Currently, most of the image segmentation algorithms are designed based
on the idea that images are partitioned into a set of regions preserving
homogeneous intra-regions and inhomogeneous inter-regions. However, human
visual intuition does not always follow this pattern. A new image segmentation
method named Visual-Hint Boundary to Segment (VHBS) is introduced, which is
more consistent with human perceptions. VHBS abides by two visual hint rules
based on human perceptions: (i) the global scale boundaries tend to be the real
boundaries of the objects; (ii) two adjacent regions with quite different
colors or textures tend to result in the real boundaries between them. It has
been demonstrated by experiments that, compared with traditional image
segmentation method, VHBS has better performance and also preserves higher
computational efficiency.Comment: 45 page
Recommended from our members
Prospect of Making Ceramic Shell Mold by Ceramic Laser Fusion
Manufacturing prototypical castings by conventional investment casting not only takes
several weeks, but also is prohibitively expensive. Z Corporation in USA, EOS GmbH and
IPT in Germany employ the techniques of 3DP and SLS respectively to make directly ceramic
shell molds for metal castings. Although those techniques dramatically reduce time
expenditure and production cost, each layer cannot be thinner than 50 µm because of using
powder to pave layers. The dimensional accuracy and roughness of the castings still cannot
meet the specification of precision casting. Therefore, in this paper the ceramic laser fusion
(CLF) was used to pave layers. Each layer can be thinner than 25 µm, so that the step effect
can be diminished and the workpiece surface can be smoother; drying time will be shortened
dramatically. Moreover, the inherent solid-state support formed by green portion has the
capability of preventing upward and downward deformation of the scanned cross sections. In
order to make shell mold which meets the roughness requirement (Rq=3.048µm) of the
precision casting, following issues have to be further studied: (1) design a proper ceramic
shell mold structure, (2) design a paving chamber for paving a complete green layer which
can be easily collapsed, (3) cut down drying time, (4) optimize laser scanning process
parameters with the smallest distortion, (5) eliminate sunken area, (6) reduce layer thickness
to less than13µm, (7) control power to guarantee the energy uniformly absorbed by workpiece,
and (8) develop a method which can directly clean green portion in cavity from gate.Mechanical Engineerin
- …