American V-King Scientific Publishing
Many networks problems in the real-world can be modeled by digraphs. In such a network, an important example of is a communication network with vertices and arcs modeling cities and communication channels, respectively. Other examples are the railroad network with vertices and arcs representing railroad stations and railways between two stations, respectively, or the World Wide Web with vertices representing Web pages, and arcs corresponding to hyperlinks between Web pages. Orthogonal factorizations in digraphs are very important in network design, circuit layout, combinatorial design, and other applications, and attract a great deal of attentions from researchers.