مجله ایرانی علوم و تکنولوژی-الف
سال:1386 | دوره:31 | شماره:2-الف |تعداد مقالات:9

The problem of combined heat and mass transfer of an electrically conducting fluid in MHD natural convection adjacent to a vertical surface is analyzed, taking into account the effects of Ohmic heating in the presence of suction or injection. An approximate numerical solution for the steady laminar boundarylayer flow over a wall of the wedge in the presence of species concentration and mass diffusion has been obtained by solving the governing equations using the numerical technique. The fluid is assumed to be viscous and incompressible. Numerical calculations are carried out for different values of dimensionless parameters and an analysis of the results obtained shows that the flow field is influenced appreciably by the magnetic effect, the buoyancy ratio between species and thermal diffusion and suction/injection at the wall surface. Effects of these major parameters on transport behaviors are investigated methodically and typical results are illustrated to reveal the tendency of the solutions. Representative results are presented for the velocity, temperature, and concentration distributions, as well as the local skin-friction coefficient and skin friction.

In this paper, we investigate some problems which can be reduced to the Goursat problem for a fourth order equation. Some results and theorems are given concerning the existence and uniqence for the solution of the suggested problem.

T. Ikawa obtained an ordinary differential equation for the circular helix. Recently, the helix have been investigated by many differential geometers such as T. Ikawa, H. Balgetir, M. Bektas, M. Ergut, N. Ekmekci and H. H. Hacisalihoglu. In this paper, making use of this author’s methods, we obtained characterizations of helix for a curve with respect to the Frenet frame in 3-dimensional Galilean space G3.

In this paper we introduce some new double sequence spaces using the Orlicz function and examine some properties of the resulting sequence spaces.

The probability of losing a customer in M/G/n/0 and GI/M/n/0 loss queuing systems with heterogeneous servers is minimized. The first system uses a queue discipline in which a customer who arrives when there are free servers chooses any one of them with equal probability, but is lost otherwise. Provided that the sum of the servers rates are fixed, loss probability in this system attains minimum value when all the service rates are equal. The second system uses queue discipline, in which a customer who enters into the system is assigned to the server with the lowest number. Loss probability in this system takes the minimum value in the case when the fastest server rule is used in which an incoming customer is served by the free server with the shortest mean service time. If the mean of the arrival distribution is fixed, then loss probability is minimized by deterministic arrival distribution.

The present paper is concerned with the generalization of the Holditch Theorem under oneparameter homothetic motion on Lorentzian planes. In this paper, for the homothetic Lorentzian motion, we expressed the Steiner formula. Furthermore, we present the Holditch-Type Theorems.