# Daphne Der-Fen Liu

• SIAM J. Discrete Math.
• 2005
For a graph G, let diam(G) denote the diameter of G. For any two vertices u and v in G, let d(u, v) denote the distance between u and v. A multi-level distance labeling (or distance labeling) for G is a function f that assigns to each vertex of G a non-negative integer such that for any vertices u and v, |f(u)− f(v)| ≥ diam(G) − dG(u, v) + 1. The span of f(More)
Let G be a connected graph with diameter diam(G). The radio number for G, denoted by rn(G), is the smallest integer k such that there exists a function f : V (G) → {0, 1, 2, · · · , k} with the following satisfied for all vertices u and v: |f(u)−f(v)| ≥ diam(G)−dG(u, v)+1, where dG(u, v) is the distancee between u and v. We prove a lower bound for the radio(More)
• Electr. J. Comb.
• 2012
The Ohba Conjecture says that every graph G with |V (G)| ≤ 2χ(G) + 1 is chromatic choosable. This paper studies an on-line version of Ohba Conjecture. We prove that unlike the off-line case, for k ≥ 3, the complete multipartite graph K2?(k−1),3 is not on-line chromatic-choosable. Based on this result, the on-line version of Ohba Conjecture is modified as(More)
• J. Comb. Theory, Ser. B
• 1999
We discuss relationships among T-colorings of graphs and chromatic numbers, fractional chromatic numbers, and circular chromatic numbers of distance graphs. We first prove that for any finite integral set T that contains 0, the asymptotic T-coloring ratio R(T ) is equal to the fractional chromatic number of the distance graph G(Z, D), where D=T&[0]. This(More)
• Discrete Mathematics
• 2000
Given a graph G and a positive integer d, an L(d; 1)-labeling of G is a function f that assigns to each vertex of G a non-negative integer such that if two vertices u and v are adjacent, then |f(u)− f(v)|¿d; if u and v are not adjacent but there is a two-edge path between them, then |f(u)−f(v)|¿1. The L(d; 1)-number of G, d(G), is de ned as the minimum m(More)
• Journal of Graph Theory
• 2004
Let Z be the set of all integers and M a set of positive integers. The distance graph G(Z,M) generated by M is the graph with vertex set Z and in which i and j are adjacent whenever |i − j| ∈ M . Supported in part by the National Science Foundation under grant DMS 9805945. Supported in part by the National Science Council, R. O. C., under grant(More)
• Ars Comb.
• 2009
Let G be a connected graph. For any two vertices u and v, let d(u, v) denote the distance between u and v in G. The maximum distance between any pair of vertices is called the diameter of G and denoted by diam(G). A radio-labeling (or multi-level distance labeling) with span k for G is a function f that assigns to each vertex with a label from the set {0,(More)