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1.
Circular Chromatic Number and Mycielski Graphs   总被引：7，自引：0，他引：7
As a natural generalization of graph coloring, Vince introduced the star chromatic number of a graph G and denoted it by *(G). Later, Zhu called it circular chromatic number and denoted it by c(G). Let (G) be the chromatic number of G. In this paper, it is shown that if the complement of G is non-hamiltonian, then c(G)=(G). Denote by M(G) the Mycielski graph of G. Recursively define Mm(G)=M(Mm–1(G)). It was conjectured that if mn–2, then c(Mm(Kn))=(Mm(Kn)). Suppose that G is a graph on n vertices. We prove that if , then c(M(G))=(M(G)). Let S be the set of vertices of degree n–1 in G. It is proved that if |S| 3, then c(M(G))=(M(G)), and if |S| 5, then c(M2(G))=(M2(G)), which implies the known results of Chang, Huang, and Zhu that if n3, c(M(Kn))=(M(Kn)), and if n5, then c(M2(Kn))=(M2(Kn)).* Research supported by Grants from National Science Foundation of China and Chinese Academy of Sciences.  相似文献
2.
Perfect Matchings of Generalized Polyomino Graphs   总被引：3，自引：0，他引：3
In this paper necessary and sufficient conditions are given for a generalized polyomino graph to have a perfect matching and to be elementary, respectively. The project was supported financially by National Natural Science Foundation of China (10431020).  相似文献
3.

4.
A heuristic algorithm for the strip packing problem   总被引：1，自引：0，他引：1
The two-dimensional strip packing problem is to pack a given set of rectangles into a strip with a given width and infinite height so as to minimize the required height of the packing. From the computational point of view, the strip packing problem is an NP-hard problem. With the B*-tree representation, this paper first presents a heuristic packing strategy which evaluates the positions used by the rectangles. Then an effective local search method is introduced to improve the results and a heuristic algorithm (HA) is further developed to find a desirable solution. Computational results on randomly generated instances and popular test instances show that the proposed method is efficient for the strip packing problem.  相似文献
5.
6.
The total chromatic number of a graph G, denoted by χ(G), is the minimum number of colors needed to color the vertices and edges of G such that no two adjacent or incident elements get the same color. It is known that if a planar graph G has maximum degree Δ≥9, then χ(G)=Δ+1. In this paper, we prove that if G is a planar graph with maximum degree 7, and for every vertex v, there is an integer kv∈{3,4,5,6} so that v is not incident with any kv-cycle, then χ(G)=8.  相似文献
7.
In this paper, we propose a method for finding a Nash equilibrium of two-person games with alternating offers. The proposed method is referred to as the inexact proximal alternating direction method. In this method, the idea of alternating direction method simulates alternating offers in the game, while the inexact solutions of subproblems can be matched to the assumptions of incomplete information and bounded individual rationality in practice. The convergence of the proposed method is proved under some suitable conditions. Numerical tests show that the proposed method is competitive to the state-of-the-art algorithms.  相似文献
8.
We propose a differential evolution-based algorithm for constrained global optimization. Although differential evolution has been used as the underlying global solver, central to our approach is the penalty function that we introduce. The adaptive nature of the penalty function makes the results of the algorithm mostly insensitive to low values of the penalty parameter. We have also demonstrated both empirically and theoretically that the high value of the penalty parameter is detrimental to convergence, specially for functions with multiple local minimizers. Hence, the penalty function can dispense with the penalty parameter. We have extensively tested our penalty function-based DE algorithm on a set of 24 benchmark test problems. Results obtained are compared with those of some recent algorithms.  相似文献
9.
Discrete sensor placement problems in distribution networks   总被引：1，自引：0，他引：1
We consider the problem of placing sensors in a network to detect and identify thesource of any contamination. We consider two variants of this problem:
(1) sensor-constrained: we are allowed a fixed number of sensors and want to minimize contaminationdetection time; and

(2) time-constrained: we must detect contamination within a given time limit and want to minimize the number of sensors required.

Our main results are as follows. First, we give a necessary and sufficient condition for source identification.Second, we show that the sensor and time constrained versions of the problem are polynomially equivalent. Finally, we show that the sensor-constrained version of the problem is polynomially equivalent to the asymmetric k-center problem and that the time-constrained version of the problem is polynomially equivalent to the dominating set problem.  相似文献

10.
We prove that a finite family ={B 1,B 2, ...,B n } of connected compact sets in d has a hyperplane transversal if and only if for somek there exists a set of pointsP={p 1,p 2, ...,p n } (i.e., ak-dimensional labeling of the family) which spans k and everyk+2 sets of are met by ak-flat consistent with the order type ofP. This is a common generalization of theorems of Hadwiger, Katchalski, Goodman-Pollack and Wenger.Supported in part by NSF grant DMS-8501947 and CCR-8901484, NSA grant MDA904-89-H-2030, and the Center for Discrete Mathematics and Theoretical Computer Science (DIMACS), a National Science Foundation Science and Technology Center, under NSF grant STC88-09648.Supported by the National Science and Engineering Research Council of Canada and DIMACS.  相似文献
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