It is well known that singular maps (i. e. ,those have only one face on a surface)play a key role in the theory of up-embeddability of graphs. In this paper the
In this paper, the variable coefficient Sine-Gordon type equation uxt=a(t)sinu+β(t)uxx+k(t)(xux)x is discussed. It is related to the eigenvalue problem Vx=QV.T
In this paper, we prove that almost all circulant digraphs are strongly connected. Furthermore, for any given positive integer m, we show that almost every circ