The track class and speed for North American railroads are governed by regulations from the Federal Railroad Administration. Better quality of track permits greater operational speeds and lower transportation cost but also requires greater maintenance expenditure. In this study, we considered...

The radiative decay of the Wannier exciton in thin crystal films is studied by the method of Heitler and Ma in the resonance approximation. It is shown that, while the broken crystal symmetry opens up the possibility of radiative decay, the correlation brought about by the interaction of the...