سال:1388 | دوره: | شماره: |تعداد مقالات:8

In this paper, by considering the notions of dual right and dual left stabilizers in bounded BCK-algebras, we obtain some related results. After that we investigate the relationship between the dual left (right) stabilizers and dual ideals in bounded BCK-algebras. Then we define a class of special bounded BCK-algebras called dual normal BCK-algebras. Finally we prove that the dual semisimple bounded BCK-algebras and dual J-semisimple bounded BCK-algebras are all dual normals.

In this paper, reproducing kernel method is presented to obtain the analytical and approximate solutions to system of ordinary differential equations with variable coefficients. The solution obtained by using the method takes the form of a convergent series with easily computable components. In the mean time, the approximate solution un(x) is obtained by the n-term intercept of the analytical solution and is proved to converge to the exact solution. Some numerical examples are studied to demonstrate the accuracy of the present method. Results obtained by the method indicate the method is simple and effective.

In this paper availability analysis of a milk-powder plant with three states– good, reduced and failed is given. Taking different failure rates and repair rates the availability of the system is evaluated. Mathematical formulation of the problem is carried out using probability considerations and the differential equations are solved using Runge-Kutta method of order four. Tables for various parameters are given which are useful to the management for predictions about the behavior of various equipments.

In this paper, the tenth-order linear special case boundary value problems are solved using the variational iteration method. The algorithm approximates the solutions, and their higher-order derivatives, of differential equations and it avoids the complexity provided by other numerical approaches. Three examples compared with those considered by Siddiqi, Twizell and Akram [S.S. Siddiqi, E.H. Twizell, Spline solutions of linear tenth order boundary value problems, Int. J. Comput. Math. 68 (1998) 345-362; S.S.Siddiqi, G.Akram, Solutions of tenth-order boundary value problems using eleventh degree spline Applied Mathematics and Computation 185 (1)(2007) 115-127] show that the method is simple and valid.

Analysis of strengths, weaknesses, opportunities and threats (SWOT) is a method to formulate the strategy. Although the SWOT analysis successfully provides the key factors of the problem, it has some drawbacks in selecting appropriate strategy for the evaluation and final decision steps. During recent years, some multiple criteria decision making (MCDM) techniques such as analytic hierarchy process (AHP) and analytic network process (ANP) remove some of these deficiencies, but the nature of these decision usually is very complex and using crisp data is not suitable. In this paper, linguistic variable represented with fuzzy numbers are used to assess the ratings and weights. Then, a MCDM model based on fuzzy sets theory is proposed to handle the strategy selection problem with imprecise data. According to the concept of the TOPSIS in multiple-criteria group decision making (MCGDM) problem, an index of closeness coefficient (CC) is defined to determine the ranking order of all strategies by calculating the distance to the both fuzzy ideal solution and fuzzy anti-ideal solution based on approach of ordering of the fuzzy numbers simultaneously. Finally, an example is given to highlight the procedure of the proposed method.

In this paper, we present a new iterative method for solving non-linear equations f(x)=0, by using Potra and Ptaks method [1]. It is shown that the order of convergence of this method is five or higher. Several numerical examples are given to illustrate the performance of the presented method.

A practical common weight goal programming methodology with an improved discriminating power for technology selection is introduced. The proposed goal programming methodology enables the evaluation of the relative efficiency of decision making units (DMUs) with respect to multiple outputs and a single exact input with common weights. Its robustness and discriminating power are illustrated via a previously reported robot evaluation problem by comparing the ranking obtained by the proposed goal programming framework with that obtained by the DEA classic model (CCR model) and Minimax method (Karsak and Ahiska (2005)).

In this paper, using orthogonally of Tchebychev polynomials, we present an orthonormal wavelet basis for L2[0, 1]. We use this basis for solving Neumann problems with Galerkin method. The property of this basis is that a variety of integral operators is represented in this basis as sparse matrices, to high precision. Some examples are solved to illustrate the efficiency and accuracy of this method.