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Engineered thin films consisting of periodic arrays of silicon microcrystallites in a hydrogenated amorphous silicon host matrix have been prepared by plasma-enhanced chemical vapor deposition where the hydrogen dilution of silane is modulated in multiple cycles. These types of films have been guided by a phase evolution diagram, depicting the deposition conditions and film thickness at which the material exhibits amorphous, microcrystalline, or mixed-phase (amorphous+microcrystalline) characteristics, developed for intrinsic Si:H prepared with varying H2 dilution on unhydrogenated a-Si:H. Real time spectroscopic ellipsometry (RTSE) has been used in situ to noninvasively determine the phase evolution of the resulting hydrogenated mixed-phase (amorphous+microcrystalline) silicon thin films and corroborated with dark-field transmission electron microscopy. Such tailored microstructures are of growing interest as components of thin film photovoltaic devices, and RTSE is shown to be a key technique for structure verification. [ABSTRACT FROM AUTHOR]

Presents a computer simulation of a one-dimensional particle migration by local hopping of Chandrasekhar type with no local bias. Concept of local particle traffic; Cases of reflecting and absorbing boundaries; Specification and evaluation of the hopping model.

A study has been made of the influence on shock spectrum curves of the interaction between a superstructure and its nonrigid foundation. Such interaction causes the spectrum values of interest to lie in the valleys corresponding to the superstructure's fixed base natural frequencies, while the peak spectrum values occur at the combined system natural frequencies. Normal mode theory for lumped mass systems is reviewed briefly and the necessary equations are presented. These equations demonstrate how shock spectrum data are applicable for calculating deflections, stresses, etc., for structures subjected to transient excitations. The concept of design shock spectra is discussed, and an example shows how design spectrum data might be applied to a particular case. [ABSTRACT FROM AUTHOR]