15,627 research outputs found
Poly[bisÂ[μ2-2-(1H-1,2,4-triazol-1-yl)acetato]zinc(II)]
In the title compound, [Zn(C4H4N3O2)2]n, the ZnII atom is coordinated by two O atoms [Zn—O = 1.969 (2) and 1.997 (2) Å] and two N atoms [Zn—N = 2.046 (2) and 2.001 (2) Å] in a distorted tetraÂhedral geometry. Non-classical interÂmolecular C—H⋯O hydrogen bonds link the complex into a three-dimensional supraÂmolecular framework
Finite automata for testing uniqueness of Eulerian trails
We investigate the condition under which the Eulerian trail of a digraph is
unique, and design a finite automaton to examine it. The algorithm is
effective, for if the condition is violated, it will be noticed immediately
without the need to trace through the whole trail
Parallel-cascade-based mechanisms for heating solar coronal loops: test against observations
The heating of solar coronal loops is at the center of the problem of coronal
heating. Given that the origin of the fast solar wind has been tracked down to
atmospheric layers with transition region or even chromospheric temperatures,
it is worthy attempting to address whether the mechanisms proposed to provide
the basal heating of the solar wind apply to coronal loops as well. We extend
the loop studies based on a classical parallel-cascade scenario originally
proposed in the solar wind context by considering the effects of loop
expansion, and perform a parametric study to directly contrast the computed
loop densities and electron temperatures with those measured by TRACE and
YOHKOH/SXT. This comparison yields that with the wave amplitudes
observationally constrained by SUMER measurements, while the computed loops may
account for a significant fraction of SXT loops, they seem too hot when
compared with TRACE loops. Lowering the wave amplitudes does not solve this
discrepancy, introducing magnetic twist will make the comparison even less
desirable. We conclude that the nanoflare heating scenario better explains
ultraviolet loops, while turbulence-based steady heating mechanisms may be at
work in heating a fraction of soft X-ray loops.Comment: 6 pages, 1 figure, to appear in proceedings of AstroNum-201
Face recognition based on improved Retinex and sparse representation
AbstractIn this paper, we proposed a method based on improved Retinex theory and sparse representation to deal with the difficulties for face recognition under inhomogeneous illumination. In our work, the total variation model was introduced to optimize the parameters of Retinex and the illumination insensitive features were extracted as the dictionary of sparse representation. Finally, the facial images could be recognized by the proposed algorithm. The experimental results on different benchmark face databases indicated that the proposed approach could be more efficient than traditional methods for face images under uncontrolled illumination conditions
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