Purpose The purpose of this paper is to calculate the back scattering response from single, finite and infinite arrays of nonlinear antennas like the case where the antennas are exposed to high-value signals such as lightning strokes. Design/methodology/approach In this paper, the authors have used a recently introduced optimization technique called intelligent water drop. Findings The results exhibit that the method used by the authors is faster and more accurate than other conventional optimization algorithms, i.e. particle swarm optimization and genetic algorithm. Originality/value A new optimization algorithm is used to solve nonlinear problem accurately and sufficiently. Although the technique is not confined to the mentioned examples in the paper, it can be applied to other nonlinear circuits.

Abstract:The PI polynomial of a molecular graph is defined to be the sum X |E(G)|−N(e) + |V(G)|(|V(G)|+1)/2 − |E(G)| over all edges of G, where N(e) is the number of edges parallel to e. In this paper, the PI polynomial of the phenylenic nanotubes and nanotori are computed. Several open questions are also included.

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PI and Szeged indices are two of the most important topological indices defined in chemistry. In this study, the PI and Szeged indices of linear [n]-phenylenes and a cyclic hexagonal-square chain consisting of n mutually isomorphic hexagonal chains were computed. The PI and Szeged indices of a multiple phenylene, which is the 2-dimensional case of a phenylenic nanotube and nanotorus, were determined.

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