The effects caused by convection and radiation heat transfer on the distribution of temperature, airflow and heat transfer in a greenhouse containing a heated solid block are studied numerically. Differential governing equations of the system are analyzed by utilized the finite volume method and the coupling of pressure-velocity is handled by the algorithm of SIMPLER. The systems algebraic equations are resolved by the conjugated of the gradient method. The greenhouse is supposed of an aspect ratio of A = 1.5, and the numerical results are presented in terms of streamlines, isotherms and Nusselt number for the range of Rayleigh numbers between 103 and 106. For the case of inlet airflow, the mixed convection of the airflow of in a greenhouse formed by two walls lateral and a roof with two symmetrical slopes were studied. The heating conditions of the walls for the greenhouse was taken as (Tc for the floor and Tf for the roof, with Tc> Tf), with openings of the cold air inlet is left-walled and the outlet is so the symmetry of right walls. The Prandtl number is set at 0.702 (for the case of air). Several situations have been considered for Rayleigh number and solid block height at fixed Reynolds number at Re = 100. The results showed that the Rayleigh number has important effect on the performance of the flow and thermal structure. Also, the isotherms and current lines is effected by varying the solid block height. In addition the local and medium Nusselt number along the hot wall increased with increasing the Rayleigh number and solid block height.

<p>A differential encrypted transceiver was designed in the signal-to-noise ratio systems. A time"-"spread" frequency-"encoded (TSFE) algorithm was proposed using the orthogonal frequency multiplexing multiplier OFDM. The proposed design was verified under the Doppler frequency effect and there was an improvement in the performance of the signal-to-noise ratio system. As a result, the reliability of decoded data was increased and achieves the ability to correct coding bits of information.</p>