Iranian Journal of Mathematical Sciences and Informatics
Volume:2 Issue: 2, Nov 2007

This paper is concerned with the effect of pure shear on the reflection from a plane boundary of infinitesimal plane waves propagating in a half-space of incompressible isotropic elastic material. For a special class of constitutive laws it is shown that an incident plane harmonic wave propagating in the considered plane gives rise to a surface wave in addition to a reflected wave (with angle of reflection equal to the angle of incidence) although its amplitude may vanish at certain discrete angles but is independent of the state of deformation. Reflected wave amplitude is exactly equal to one in this case.For a second class of constitutive laws similar behavior is found for certain combinations of angle of incidence, material properties and deformations, but additional possibilities also arise. In particular, there may be two reflected waves instead of one reflected wave and a surface wave. Here surface wave amplitude depends upon the pure shear and the reflected wave amplitude is not equal to one in general.The dependence of the amplitudes of the reflected, and surface waves on the angle of incidence, the states of deformation is illustrated graphically.

Dendritic macromolecules’ have attracted much attention as organic examples of well-defined nanostructures. These molecules are ideal model systems for studying how physical properties depend on molecular size and architecture. In this paper using a simple result, some GAP programs are prepared to compute Wiener and hyper Wiener indices of dendrimers.

Let G be the chemical graph of a molecule. The matrix D = [dij] is called the detour matrix of G, if dij is the length of longest path between atoms i and j. The sum of all entries above the main diagonal of D is called the detour index of G. In this paper, a new algorithm for computing the detour index of molecular graphs is presented. We apply our algorithm on copper and silver nanoclusters to find their detour index.

Let G = (V,E) be a simple graph with exactly n vertices and m edges. The aim of this paper is a new method for investigating nontriviality of the automorphism group of graphs. To do this, we prove that if |E| >=[(n - 1)2/2] then |Aut(G)|>1 and |Aut(G)| is even number.

In this paper, we propose a genetic algorithm, called GenSPN, for finding highly probable differential characteristics of substitution permutation networks (SPNs). A special fitness function and a heuristic mutation operator have been used to improve the overall performance of the algorithm. We report our results of applying GenSPN for finding highly probable differential characteristics of Serpent block cipher. A comparison of the resultant characteristics with the previously published works shows that GenSPN can find differential characteristics of higher probabilities.