Iranian Journal of Mathematical Sciences and Informatics
Year:2008 | Volume:3 | Issue:1|Papers Count:7

The Wiener index of a graph Gis defined as W(G) =1/2 S {i.j}Í v(G)  d (i.j) where V (G) is the set of vertices of G and d(i, j) is the distance between vertices i and j. In this paper, we give an algorithm by GAP program that can be compute the Wiener index for any graph; also we compute the Wiener index of HAC5C7[p, q] and HAC5C6C7[p, q] nanotubes by this program.

The character table of the fully nonrigid water cluster (cyclic forms), (H2O)i, with Cih symmetry derived for the first time, for 2£i£6. The group of all feasible permutations is the wreath product of groups Si[S2] which consists of i!2i operations for i!2i, ..., 6 divided into ( w.r.t) 5, 10, 20, 36, 65 conjugacy classes and 5, 10, 20, 36, 65 irreducible representations respectively. We compute the full character table of (H2O)2, (H2O)3, (H2O )4, (H2O)5  and (H2O)6.

The edge version of Szeged index and vertex version of PI index are defined very recently. They are similar to edge-PI and vertex-Szeged indices, respectively. The different versions of Szeged and PIindices are the most important topological indices defined in Chemistry. In this paper, we compute the edge-Szeged and vertex-PIindices of some important classes of benzenoid systems.

The Merrifield-Simmons index of a graph is defined as the total number of the independent sets of the graph and the Hosoya index of a graph is defined as the total number of the matchings of the graph. In this paper, we give formula for Merrifield-Simmons and Hosoya indices of some classes of cartesian product of two graphs K2×H, where H is a path graph Pn, cyclic graph Cn, or star graph Sn, with n vertices (These are called: ladder graph, prism graph, and book graph).

The vertex version of PI index is a molecular structure descriptor which is similar to vertex version of Szeged index. In this paper, we compute the vertex-PI index of TUC4C8(S), TUC4C8(R) and HAC5C7[r, p].

In this paper we try to put different practical aspects of the general linear methods discussed in the papers [1,6,7] under one algorithm to show more details of its implementation. With a proposed initial step size strategy this algorithm shows a better performance in some problems. To illustrate the efficiency of the method we consider some standard test problems and report more useful details of step size and order changes, and number of rejected and accepted steps along with relative global errors.

In this paper, a fuzzy production inventory model with resalable returns has been analysed in an imprecise and uncertain environment by considering the cost and revenue parameters as trapezoidal fuzzy numbers. The main objective is to determine the optimal fuzzy production lotsize which maximizes the expected profit where the products leftout at the end of the period are salvaged and demands which are not met directly are lost. The modified graded mean integration epresentation method is used for defuzzification of fuzzy parameters of production lotsize and expected profit. An example is presented to illustrate the method applied in the model.