Abstract. This paper deals with an approximative solution in the analytical form of some second order linear differential equation with time depend parameters. The analytic solution is compared with the numerical solution obtained by Runge-Kutta method and the conditions of the convergence of this analytical method are discussed.

No abstract

No abstract

Abstract. In this article we study the behavior of solutions to the system of delay differential equations...where the coefficients p i may have zeros, and the components of the solution may change signs. We prove properties to the components of the solutions as t approaches infinity.

Euler-Lagrange optimization method is exploited here to develop energy saving position control strategy valid for a.c. drives. The optimization principle respects copper losses minimization only. Boundary value problem for Euler-Lagrange equations is solved by Differential transformation method (DTM).