• Journal of applied mathematics & informatics
• /
• v.5 no.1
• /
• pp.65-72
• /
• 1998

Many optimization problems like domination and Steiner tree are NP-complete on chordal graphs but can be solved in polyno-mial time on doubly chordal graphs. Investigating properties of dou-bly chordal graphs probably help to design efficient algorithms for the graphs. We present some characterizations of dobly chordal graphs which are based on clique matrices and neighborhood matrics also men-tioned how a doubly perfect elimination ordering of a doubly chordal graph can be computed from the results.

• School Mathematics
• /
• v.7 no.4
• /
• pp.353-373
• /
• 2005

The purpose of this paper is to analysis the basic network problem which can be applied to the mathematically gifted students in elementary school. Mainly, we discuss didactic transpositions of the double counting principle, the game of sprouts, Eulerian graph problem, and the minimum connector problem. Here the double counting principle is related to the handshaking lemma; in any graph, the sum of all the vertex-degree is equal to the number of edges. The selection of these subjects are based on the viewpoint; to familiar to graph theory, to raise algorithmic thinking, to apply to the real-world problem. The theoretical background of didactic transpositions of these subjects are based on the Polya's mathematical heuristics and Lakatos's philosophy of mathematics; quasi-empirical, proofs and refutations as a logic of mathematical discovery.

• KSII Transactions on Internet and Information Systems (TIIS)
• /
• v.9 no.5
• /
• pp.1662-1681
• /
• 2015

The efficient send and receive of information in VANET improves the efficiency of the safety and traffic services advertisment and discovery. However, if the V2V is the only communication system used, the restrictions of the urban environment and network drop the performance of VANET. In order to improve the performance of the network, it is necessary to use V2I communication as well as V2V communication. Therefore, RSUs must be placed in the environment. However due to the high costs of placement, the full coverage of the environment would not be possible. Therefore, it is necessary to optimally install a limited number of RSUs in the environment.

• Journal of information and communication convergence engineering
• /
• v.19 no.2
• /
• pp.114-119
• /
• 2021

This paper proposes a method to find an optimal T' with the most terminal of the subset of T' trees that can be connected by a given length by improving a memetic genetic algorithm within several constraints, when the set of terminal T is given to the Euclidean plane R². Constraint (1) is that a given length cannot connect all terminals of T, and (2) considers only the rectilinear layout of the edge connecting each terminal. The construction of interconnections has been used in various design-related areas, from network to architecture. Among these areas, there are cases where only the rectilinear layout is considered, such as wiring paths in the computer network and VLSI design, network design, and circuit connection length estimation in standard cell deployment. Therefore, the heuristics proposed in this paper are expected to provide various cost savings in the rectilinear layout.

• Journal of the Institute of Electronics Engineers of Korea TC
• /
• v.48 no.2
• /
• pp.6-13
• /
• 2011

This paper deals with the interconnection problem in ad-hoc networks or sensor networks, where relay nodes are deployed additionally to form connections between given nodes. This problem can be reduced to a NP-hard problem. The nodes of the networks, by applications or geographic factors, can be deployed densely in some areas while sparsely in others. For such a case one can make an approximation scheme, which gives shorter execution time, for the additional node deployments by ignoring the interconnections inside the dense area of nodes. However, the case is still a NP-hard, so it is proper to establish a polynomial time approximation scheme (PTAS) by implementing a dynamic programming. The analysis can be made possible by an elaboration on making the definition of the objective function. The objective function should be defined to be able to deal with the requirement incurred by the substitution of the dense area with its abstraction.