My research interests are in graph theory and combinatorics. In particular, I am interested in global substructures of graphs. For example, I have obtained several results in the following subjects. (1) Edge contraction preserving the connectivity: in particular, I obtained several results on contractible edges in 3-connected graphs, and posed a noticeable conjecture which is still open. (2) Factors in graphs: this is the study of finding sufficient conditions for a graph to have a spanning subgraph with constraints on degrees or on components. (3) Paths and cycles in graphs: research on the existence of paths and cycles passing through given vertices and/or edges, on decomposing the vertex set into cycles and/or paths with certain prescribed conditions. (4) Graphs on surfaces: I am interested in combinatorial properties of graphs on surfaces, in particular properties related to hamiltonicity.
Also, I obtained several result on extremal set theory and discrete geometry.