Power electronic converters are non-linear time-dependent systems whose exact analysis without the use of computers is very difficult, and even using computer softwares requires a long time. Use of the state space averaging method, as will be mentioned, in addition to simplifying the analysis procedure which is a result of converting a time-dependent system to a time-independent one, reduces th...

Power electronic converters are non-linear time-dependent systems whose exact analysis without the use of computers is very difficult, and even using computer softwares requires a long time. Use of the state space averaging method, as will be mentioned, in addition to simplifying the analysis procedure which is a result of converting a time-dependent system to a time-independent one, reduces th...

magnetotelluric (mt) method is an important passive surface geophysical method which uses the earth’s natural electromagnetic fields to investigate the electrical resistivity structure of the subsurface. the depth of investigation of mt is much higher than that of other electromagnetic (em) methods (vozoff, 1991). for a general conductivity distribution in the earth, the horizontal electric fie...

Endobronchial tuberculosis and chest radiography I read, with interest, the article entitled “Clinical and Para-clinical Presentations of Endobronchial Tuberculosis” by Ahmadi Hoseini H. S. et al. (1) published in this journal. I would like to focus on some details about the chest X-ray of patients as elaborated by the authors in the results section. Accordingly, the findings of chest radiograp...

an attempt is made for the first time to solve the quadratic and cubic model of magneto hydrodynamic poiseuille flow of phan-thein-tanner (ptt). series solution of magneto hydrodynamic (mhd) flow is developed by using homotopy perturbation method (hpm). results are presented graphically and the effects of non-dimensional parameters on the flow field are analyzed. the results obtained reveals ma...