Giant stop bands and defect modes in one-dimensional waveguide with dangling side branches

We investigate both the photonic and electronic band structure of a comb-like waveguide geometry in which dangling side branches are grafted along an infinite one-dimensional waveguide. In a periodic (superlattice like) waveguide, we report the opening-up of stop bands which originate both from the periodicity of the system and the resonant states of the grafted branches (which play the role of resonators). Wide gaps (narrow bands) can be obtained by grafting several dangling side branches at every node. The stop bands still remain even for identical constituent materials. We also propose a tandem structure composed of two or several successive combs which differ by their physical characteristics that allows an ultrawideband filter. This behavior results from the superposition of the bandgaps in the successive structures. The presence of a defect branch in the comb can give rise to localized modes inside gaps. These states appear as very narrow peaks in the transmission spectrum and therefore may have useful applications in the frame of photonic bandgap materials or electronic band engineering of nanostructures.     

Simulation of the effects of atmospheric scintillation on digital transmissions at centimeter and millimeter wavelengths

This paper describes the simulation of the effects of scintillation on digital transmissions. The scintillation is modelled by atmospheric turbulent cells whose parameters are determined by comparison with measured scintillation events. The effects of the cells crossing the communication link on the amplitude of the received signal are calculated as well as the transfer function. A complete communication link is simulated and the BER is calculated for different frequencies. The model can be used up to 100 GHz but this paper is focused on frequencies presently used in satellite communications.     

Natural convection of non-Newtonian fluids in a horizontal porous layer

Heat and Mass Transfer - The buoyancy-induced flows of non-Newtonian fluids in a horizontal fluid saturated porous layer is studied analytically and numerically using the power-law model to...