singular perturbation problems have been studied by many mathematicians. since the approximate solutions of these problems are as the sum of internal solution (boundary layer area) and external ones, the formation or non-formation of boundary layers should be specified. this paper, investigates this issue for a singular perturbation problem including a first order differential equation with gen...

Let k ≥ 2 and n ≥ 1 be integers, let G be a graph of order n with minimum degree at least k + 1. Let v1, v2, · · · , vk be k distinct vertices of G, and suppose that there exist k vertex disjoint cycles C1, · · · , Ck in G such that vi ∈ V (Ci) for each 1 ≤ i ≤ k. Suppose further that the minimum value of the sum of the degrees of two nonadjacent distinct vertices is greater than or equal to n ...

A computer program for the aerodynamic design and analysis of airfoils is described. This program is intended for use in an undergraduate aerospace engineering curriculum. It allows the students to interactively change the airfoil shape, thickness and camber as well as flight conditions, and allows the student to design airfoils subject to a specified pressure distribution over the surface. The...

The authors obtain necessary and sufficient conditions for the existence of oscillatory solutions with a specified asymptotic behavior of solutions to a nonlinear neutral differential equation with distributed delay of third order. We give new theorems which ensure that every solution to be either oscillatory or converges to zero asymptotically. Examples dwelling upon the importance of applicab...

We study the possibility of the finite time singularity for the 3D incompressible Navier-Stokes equations for ‘large’ force or for small viscosity if the initial velocity satisfies the the condition of initial amplification of the enstrophy. In the case of zero external force, the condition for initial data leading to finite time singularity for small viscosity is specified by some conditions o...

INTRODUCTION: The appropriate-use optimization of the limited spaces of the Iranian hospitals is believed to be a crucial step towards promoting the efficiency of these healthcare centers. The issue determining the optimization patterns of the layout of units has led to a lot of efforts by researchers as it increases the efficiency of the hospitals through patients’ improvement, changing the lo...