pulse-width modulated (pwm) adjustable frequency drives (afds) are extensively used in industries for control of induction motors. it has led to significant advantages in terms of the performance, size, and efficiency but the output voltage waveform no longer remains sinusoidal. hence, overshoots, high rate of rise, harmonics and transients are observed in the voltage wave. they increase voltag...

this paper addresses the combined effects of couple stresses, thermal radiation, viscous dissipation and slip condition on a free convective flow of a couple stress fluid induced by a vertical stretching sheet. the cogley- vincenti-gilles equilibrium model is employed to include the effects of thermal radiation in the study. the governing boundary layer equations are transformed into a system o...

A method for computing the stress-energy tensor for the quantized, massless, spin 12 field in a general static spherically symmetric spacetime is presented. The field can be in a zero temperature state or a non-zero temperature thermal state. An expression for the full renormalized stress-energy tensor is derived. It consists of a sum of two tensors both of which are conserved. One tensor is wr...

This article presents an exact solution for an axisymmetric functionally graded piezoelectric (FGP) rotating disk with constant thickness subjected to an electric field and thermal gradient. All mechanical, thermal and piezoelectric properties except for Poisson’s ratio are taken in the form of power functions in radial direction. After solving the heat transfer equation, first a symmetric dist...

In this study, the effect of the tube material on the thermal stress generated in a vertical shell and tube heat exchanger is investigated. Shell and tube heat exchangers are the most common heat exchangers used in industries. One of the most common failures in these exchangers in the industry is the tube failure at the junction of the tube to tubesheet. When the shell side and the tube side fl...

productivity of an oil well is an important parameter in any oil field development. low production rate of the wells, impose more production wells drilling which directly jeopardizes the economical feasibility of the project. oil production rate in some of the wells is very low due to low permeability of the reservoir rock. several practice like hydraulic fracturing and acid fracturing is very ...

This paper deals with the determination of the effect of varying material properties on the value of the stress intensity factors, KI and KII, for anisotropic plates containing cracks and subjected to a temperature change. Problems involving cracks and body forces, as well as thermal loads are analysed. The quadratic isoperimetric element formulation is utilized, and SIFs may be directly obtain...

one of the effective methods to improve the thermal efficiency of solar collectors is using nanofluids as the coolant. the present study experimentally investigated the effect of sio2/water nanofluid with 1% mass fraction on the performance of a symmetric collector, i.e. conical solar collector. the conical solar collector with 1 m2 area and normal to the earth was tested in ahvaz, a city in th...