Photoluminescence (PL) measurements have been performed on the nanocomposites of higher fullerene-coupled porous silicon (PS) nanocrystals. For the C70PS and C76(78)PS nanocomposites, the PL spectra show a pinning wavelength at approximately 565 nm and for the C84PS and C94PS nanosystems the pinning wavelength is at approximately 590 nm. The PL pinning property is closely related to the sorts of the coupled fullerenes. A band mixing model of direct and indirect gaps in a nanometer environment consisting of nc-Si core, SiO2 surface layer, and coupled fullerene has been proposed for calculation of electronic states. Good agreement is achieved between the experiments and theory.

There are difficulties in tracking the ceiling jet front while carrying out hot smoke tests in long tunnels with a small fire. In this study, an experimental method using infrared beams is suggested. The arrival time of the hot ceiling jet front to a designated position is measured by the abrupt attenuation of the infrared beam intensity. Field measurements are carried out in an underground tunnel of length 88 m. Diesel pool fires up to 1.5 MW are studied. The results on tracking the ceiling jet front are compared with the measurements by using the thermocouples, thermal resistors, and visual observations. This method is demonstrated to be useful for tracking the ceiling jet front at positions further away from the fire. Therefore, the method is suitable for studying the ceiling jet in hot smoke tests for evaluating smoke management systems in long tunnels.