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931.
932.
933.
We give an inequality for the group chromatic number of a graph as an extension of Brooks’ Theorem. Moreover, we obtain a structural theorem for graphs satisfying the equality and discuss applications of the theorem. 相似文献
934.
935.
936.
937.
简略介绍了“尾流”效应(wakeeffect)的等离子体模型,并依之模拟计算了1.915MeVH、2.060MeVH在100A碳膜中分解后0°方向的能谱形式。给出了相同条件下的实验结果,将两者做了比较。 相似文献
938.
Simona Lai Emanuela Locci Giuseppe Saba Ivan Husu Giancarlo Masci Vittorio Crescenzi Adolfo Lai 《Journal of polymer science. Part A, Polymer chemistry》2003,41(20):3123-3131
Dry and hydrated poly(vinyl alcohol) (PVA) gels with 55% (a‐PVA) and 61% (s‐PVA) syndiotacticity and related PVA/lactyl chitosan (LC) blends have been investigated with 129Xe and cross‐polarization/magic‐angle‐spinning 13C NMR techniques. Although the dry gels exhibit two broad 129Xe resonances in the slow‐to‐intermediate exchange limit, both hydrated gels show three resonances. The corresponding dry blends exhibit two signals, the chemical shifts and line widths of which change with respect to those of pure PVA, whereas one (a‐PVA/LC) or two (s‐PVA/LC) signals appear in the spectra of the hydrated blends. A comparative analysis of the data demonstrates that LC rearranges the domains of the polymeric matrix in both the dry and hydrated blends according to the syndiotacticity of the PVA chains. Information on the molecular motions of the amorphous and swollen polymeric domains in the kilohertz range has been obtained from an analysis of the spin‐lattice relaxation times. These data indicate that the dynamics and arrangement of the PVA chains in the gels are strongly affected by their tacticity and the addition of the copolymer LC. © 2003 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 41: 3123–3131, 2003 相似文献
939.
Tutte conjectured that every 4-edge-connected graph admits a nowhere-zero Z
3-flow and Jaeger et al. [Group connectivity of graphs–a nonhomogeneous analogue of nowhere-zero flow properties, J. Combin.
Theory Ser. B 56 (1992) 165-182] further conjectured that every 5-edge-connected graph is Z
3-connected. These two conjectures are in general open and few results are known so far. A weaker version of Tutte’s conjecture
states that every 4-edge-connected graph with each edge contained in a circuit of length at most 3 admits a nowhere-zero Z
3-flow. Devos proposed a stronger version problem by asking if every such graph is Z
3-connected. In this paper, we first answer this later question in negative and get an infinite family of such graphs which
are not Z
3-connected. Moreover, motivated by these graphs, we prove that every 6-edge-connected graph whose edge set is an edge disjoint
union of circuits of length at most 3 is Z
3-connected. It is a partial result to Jaeger’s Z
3-connectivity conjecture.
Received: May 23, 2006. Final version received: January 13, 2008 相似文献
940.