FT-i.r. study of molecular interactions of olefins with oxide surfaces
Abstract The FT-i.r. spectra of ethylene, propylene, 1-butene, cis-2-butene and trans-2-butene adsorbed on amorphous silica at 200 K, on NaY-zeolite at 220 K and on TiO2 at 300 K have been recorded. In such conditions only molecular adsorption is detected, thought to take place on the surface hydroxy groups of silica, whose νOH band is correspondingly perturbed, and on Na+ and Ti4+ exposed sites of NaY-zeolite and titania respectively. The spectra show that characteristic frequency and intensity perturbations and i.r.-activation of normally forbidden modes occur, which may be utilized to distinguish such molecular adsorbed species from the products of reactive adsorption.
Frequency offset affects the performance of orthogonal frequency division multiplexing system. The FRFT based OFDM is considered in this article to minimize this affect. The expressions of signal to interference ratio (SIR) due to inter carrier interference (ICI) has been derived for frequency selective fading channel and doubly selective fading channels (Time frequency selective fading channels) for FRFT based OFDM system. The simulation analysis validate that FRFT based OFDM systems has superior SIR performances by choosing the optimal fractional factor than the standard OFDM system, for a large carrier offset exists in the system.