共查询到20条相似文献,搜索用时 31 毫秒
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Two classes of edge domination in graphs 总被引:2,自引:0,他引:2
Baogen Xu 《Discrete Applied Mathematics》2006,154(10):1541-1546
Let (, resp.) be the number of (local) signed edge domination of a graph G [B. Xu, On signed edge domination numbers of graphs, Discrete Math. 239 (2001) 179-189]. In this paper, we prove mainly that and hold for any graph G of order n(n?4), and pose several open problems and conjectures. 相似文献
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Improved bounds for acyclic chromatic index of planar graphs 总被引:1,自引:0,他引:1
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Adrian Kosowski 《Discrete Applied Mathematics》2009,157(2):321-329
Motivated by wavelength-assignment problems for all-to-all traffic in optical networks, we study graph parameters related to sets of paths connecting all pairs of vertices. We consider sets of both undirected and directed paths, under minimisation criteria known as edge congestion and wavelength count; this gives rise to four parameters of a graph G: its edge forwarding index π(G), arc forwarding index , undirected optical index , and directed optical index .In the paper we address two long-standing open problems: whether the equality holds for all graphs, and whether indices π(G) and are hard to compute. For the first problem, we give an example of a family of planar graphs {Gk} such that . For the second problem, we show that determining either π(G) or is NP-hard. 相似文献
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Jonathan Lenchner 《Discrete Applied Mathematics》2011,159(7):612-620
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Sachin Gautam Ashish Kumar Srivastava Amitabha Tripathi 《Discrete Applied Mathematics》2008,156(12):2423-2428
Given graphs , where k≥2, the notation
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