An analytic geometry-variant approach to line ratio enhancement above the optically thin limit

We describe a simple theoretical model to investigate the anomalous effects of opacity on spectral line ratios, as previously studied in elements such as Fe XV and Fe XVII. The model developed is general: it is not specific to a particular atomic system, thus giving applicability to a number of coronal and chromospheric plasmas; furthermore, it may be applied to a variety of astrophysically relevant geometries. The analysis is underpinned by geometrical arguments, and we outline a technique for it to be used as a tool for the explicit diagnosis of plasma geometry in distant astrophysical objects.

Enhancement of dielectric constant and associated coupling of polarization behavior in thin film relaxor superlattices

Thin film capacitor structures in which the dielectric is composed of superlattices of the relaxors [0.2Pb(Zn1/3Nb2/3)O- 3-0.8BaTiO(3)] and Pb(Mg1/3Nb2/3)O-3 have been fabricated by pulsed laser deposition. Superlattice wavelength (Lambda) was varied between similar to3 and similar to 600 nm, and dielectric properties were investigated as a function of Lambda. Progressive enhancement of the dielectric constant was observed on decreasing Lambda, and, in contrast to previous work, this was not associated with the onset of Maxwell-Wagner behavior. Polarization measurements as a function of temperature suggested that the observed enhancement in dielectric constant was associated with the onset of a coupled response. The superlattice wavelength (Lambda =20 nm) at which coupled functional behavior became apparent is comparable to that found in literature for the onset of coupled structural behavior (between Lambda =5 nm and Lambda =10 nm). (C) 2001 American Institute of Physics.

Comparison of Image Transform-Based Features for Visual Speech Recognition in Clean and Corrupted Videos

We present results of a study into the performance of a variety of different image transform-based feature types for speaker-independent visual speech recognition of isolated digits. This includes the first reported use of features extracted using a discrete curvelet transform. The study will show a comparison of some methods for selecting features of each feature type and show the relative benefits of both static and dynamic visual features. The performance of the features will be tested on both clean video data and also video data corrupted in a variety of ways to assess each feature type's robustness to potential real-world conditions. One of the test conditions involves a novel form of video corruption we call jitter which simulates camera and/or head movement during recording.