It is well known that heterojunction bipolar transistors (HBTs) fabricated in the AlGaAs/GaAs material system have great potential as high-power microwave amplifiers. Power levels of 2.5 W at C band and 2.5 W at X band have already been demonstrated in devices on GaAs substrates.“* Power densities of up to 4 W/mm of emitter length in continuous wave (cw) operation have also been reported.3 GaAs...

The objectives in the cold rolling process include improved sheet surface quality, enhanced steel mechanical strength, and better solidification operations. Given the increasing demand for higher steel...

In present work, numerical analysis of three novel PEM fuel cells with tubular geometry was conducted. Tree different cross section was considered for PEM, namely: circular, square and triangular. Similar boundary and operational conditions is applied for all the geometries. At first, the obtained polarization curve for basic architecture fuel cells was validated with experimental data and then...

With respect to the limitations of fossil energy resources, different types of electric vehicles (EVs) are developed as suitable alternatives. Lithium-ion (Li-ion) battery cells play an extremely important role in EVs due to their unique features. But they need a thermal management system (TMS) to maintain their surface temperature uniformity and avoid them from thermal runaways. In the current...

A mathematical model is developed and tested with plant data for the ammonia cold shot converter of Razi Petrochemical Complex. The model is based on a material and energy balance in a differential element of beds and is subjected to the assumptions of uniform distribution of temperature and composition through a general cross section and negligible mass and heat transfer in axial direction. Th...

We studied the effect of low-pass band filters on the dynamics of a nonisothermal autocatalator as seen through feedback on a system parameter. Filters were created by selecting Fourier coefficients for the modes in the pass band according to a uniform distribution. Numerical simulations over many realizations of feedback were compared to theoretical predictions for the feedback size as a funct...

The ecliptic elongation of the moon with respect to the sun does not show uniform distribution on the birth dates of the 704 soccer players selected for the 1998 World Cup. However, a uniform distribution is expected on astronomical grounds. The World Cup players show a very pronounced tendency (p = 0.00001) to be born on days when the sun and moon are in adjacent zodiacal signs.

We consider a sequence of independent and identicaly distributed (iid) random variables with absolutely continuous distribution function F(x) and probability density function (pdf) f(x). Let Rnl be the largest observation after observing nth record and R(ns) be the smallest observation after observing the nth record. Then we say Wnr = Rnl− R(ns), n > 1, as the nth record range. We will c...