Resonant coupling between surface vibrations and electronic states in silicon nanocrystals at the strong confinement regime.

A striking correlation between infrared photoinduced absorption spectra and the photoluminescence from silicon nanocrystals indicates that quantized electronic sublevels of the nanocrystals are resonantly coupled to surface vibrational modes via a polarization field produced by coherent longitudinal polar vibrations. Our experimental results and model support the assumption that the mechanism responsible for the efficient photoluminescence from silicon nanocrystals should be assigned to inhibition of nonradiative channels rather than enhancement of radiative channels.

IDARC - BRIDGE : A computational platform for seismic damage assessment of bridge structures

This report presents the theoretical background of a computer platform for three-dimensional inelastic analysis of bridge structures. IDARC-BRIDGE utilizes recent developments by the authors and other researchers involved in the current and related NCEER projects. The program adapts and extends some of the component and damage models of the existing platform for two-dimensional analysis of buildings IDARC-2D (Kunnath et.al, 1987, Valles et. al, 1996). A number of unique features, however, expand its range of applicability to include bridge structures, which often present unusual and uncommon modeling problems. Two distinct goals define the scope of IDARC-BRIDGES: 1) to serve as an efficient and user-friendly analytical tool for investigating the behavior of bridge structures by engineers and researchers, and 2) to provide a framework for future software development by allowing the user to incorporate new modules, element types and component models or replace the existing ones.(AU)