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- Han Hyuk Cho, Suh-Ryung Kim
- Discrete Applied Mathematics
- 2005

Let D be an acyclic digraph. The competition graph of D has the same set of vertices as D and an edge between vertices u and v if and only if there is a vertex x in D such that (u, x) and (v, x) are arcs of D. In this paper, we show that the competition graphs of doubly partial orders are interval graphs. We also show that an interval graph together with… (More)

- Han Hyuk Cho, Suh-Ryung Kim, J. Richard Lundgren
- Discrete Mathematics
- 2002

- Han Hyuk Cho, Suh-Ryung Kim
- Discrete Mathematics
- 2005

- Han Hyuk Cho, Suh-Ryung Kim, Yunsun Nam
- Discrete Applied Mathematics
- 2000

The competition graph of a digraph was introduced by Cohen in 1968 associated with the study of ecosystems. Since then, the competition graph has been widely studied and many variations have been introduced. In this paper, we de ne and study the m-step competition graph of a digraph which is another generalization of competition graph. ? 2000 Elsevier… (More)

- Han Hyuk Cho, Suh-Ryung Kim, Yunsun Nam
- Ars Comb.
- 2005

- Han Hyuk Cho, Suh-Ryung Kim, Jung Yeun Lee
- Discrete Mathematics
- 2006

- Han Hyuk Cho
- Fuzzy Sets and Systems
- 1999

- ZHOU BO, HAN HYUK CHO
- 2004

Let IBn be the set of all irreducible matrices in Bn and let SIBn be the set of all symmetric matrices in IBn. Finding an upper bound for the set of indices of matrices in IBn and SIBn and determining gaps in the set of indices of matrices in IBn and SIBn has been studied by many researchers. In this paper, we establish a best upper bound for the set of… (More)

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