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Combinatorial conditions on a set of cycles of fixed degree inS n are studied, so that they generateA n orS n . It is shown thatA n orS n is so generated if and only if a graph associated with the set of cycles is connected, provided two of the cycles satisfy certain, not too restrictive, criteria. As a corollary, the minimum number of cycles of degreem ≧ 2 that generateA n or Sn is determined. 相似文献
86.
K.B. Reid 《Discrete Mathematics》1982,38(1):93-98
A king in a tournament is a vertex which can reach every other vertex via a 1-path or 2-path. A new inductive proof is given for the existence of an n-tournament with exactly k kings for all integers n ? k ? 1 with the following exceptions: k = 2 with n arbitrary, and n = k = 4 (in which cases no such n-tournament exists). Also, given an n-tournament T, the smallest order m is determined so that there exists an m-tournament W which contains T as a subtournament and so that every vertex of W is a king. Bounds are obtained in a similar problem in which the kings of W are exactly the vertices of T. 相似文献
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88.
Measurements of the electrofission cross section for 232Th, 238U and 237Np have been made for an electron energy range from 20 to 120 MeV. A comparison is made between the electrofission and photofission cross sections using the concept of virtual photons. It is deduced that the electrofission reaction for these elements proceeds through a significant E2 contribution as well as an E1 transition mode. 相似文献
89.
Pullman [3] conjectured that if k is an odd positive integer, then every orientation of a regular graph of degree k has a minimum decomposition which contains no vertex which is both the initial vertex of some path in the decomposition and the terminal vertex of some other path in the decomposition. In this paper, the conjecture is established for cubic graphs, and its connection with Kelly's conjecture for tournaments is described. 相似文献
90.
The hyperfine coupling tensors of muonated radicals in a large single crystal of benzophenone have been determined by measuring
the hyperfine couplings of the radicals as the crystal was rotated about three orthogonal axes.
Signals from four radicals were observed, corresponding to the four molecules per unit cell in the crystal. Due to an ambiguity
in the data we are unable to discriminate between two similar hyperfine coupling tensors. Both lead to an isotropic hyperfine
coupling of \sim32 MHz, contrasting with the solution value of 42 MHz obtained earlier in diethyl ether. The anisotropic components
of the tensor are relatively large, at approximately -15 MHz, -6 MHz and 21 MHz, respectively.
This revised version was published online in August 2006 with corrections to the Cover Date. 相似文献