Here, the capability of the SC-EAHE system to meet the required thermal needs of individuals and also the dependence of the system performance on environmental and geometrical issues, have been studied. To determine the heat transfer characteristics of the system, a mathematical model based on energy conservation equations has been developed and solved by an iterative method. The results of study for the effect of air gap size variation on the air change per hour (ACH) at various solar radiation values shows that this effect (air gap depth on the ACH) is significant up to 0.2 (m), and the ACH and room air temperature remains almost constant beyond the 0.2 (m). The results also revealed that the design of EAHE with the diameter of 0.5 (m) would lead to the best performance. It is found that, with proper insulation, SC system can provide thermal comfort condition even at the ambient temperature as low as 5 o C and the solar radiation intensity of 185 (w/m 2).

In this study using two low-energy systems to enhance passive cooling and natural ventilation in a solar room have been compared. First system consists of a Solar Chimney (SC) and an Evaporative Cooling Cavity (ECC) and the second one includes a Solar Chimney (SC) and an Earth-to-Air Heat exchanger (EAHE).To determine the heat and mass transfer characteristics of the systems, a mathematical model based on conservation equations of mass and energy has been developed and solved by an iterative method. The findings show that when the cooling demand of the room is 116W and the relative humidity is lower than 50%, the SC-ECC system can make acceptable indoor air conditioning even at ambient 40 o C, with weak solar intensity of 200 W/m 2 . It is also found that, the proposed system can provide thermal comfort conditions even during the night with zero solar radiation. The results about SC-EAHE system show that when the ambient temperature and cooling demand are high (1500W), proper configurations could provide good indoor condition even at poor solar intensity of 100 W/m 2 and high ambient air temperature of 50 o C. Comparative survey shows the SC-EAHE system is the best choice for buildings with poor insulation at day time, but SC-ECC system is better for night ventilation and cooling purposes especially in arid climates.

Microwave holography technique reconstructs a target image using recorded amplitudes and phases of the signals reflected from the target with Fast Fourier Transform (FFT)-based algorithms. The reconstruction algorithms have two or more steps of two- and three-dimensional Fourier transforms, which have a high computational load. In this paper, by neglecting the impact of target depth on image reconstruction, an efficient Fresnel-based algorithm is proposed, involving only one-step FFT for both single- and multi-frequency microwave imaging. Numerous tests have been performed to show the effectiveness of the proposed algorithm including planar and non-planar targets, using the raw data gathered by means of a scanner operating in X-band. Finally, a low-cost and high-speed hardware architecture based on fixed-point arithmetic is introduced which reconstructs the planar targets. This pipeline architecture was tested on field programmable gate arrays operating at 200 MHz clock frequency, which illustrates more than 30 times improvement in computation time compared with a computer.