380 research outputs found
Adaptive filtering of radar images for autofocus applications
Autofocus techniques are being designed at the Jet Propulsion Laboratory to automatically choose the filter parameters (i.e., the focus) for the digital synthetic aperture radar correlator; currently, processing relies upon interaction with a human operator who uses his subjective assessment of the quality of the processed SAR data. Algorithms were devised applying image cross-correlation to aid in the choice of filter parameters, but this method also has its drawbacks in that the cross-correlation result may not be readily interpretable. Enhanced performance of the cross-correlation techniques of JPL was hypothesized given that the images to be cross-correlated were first filtered to improve the signal-to-noise ratio for the pair of scenes. The results of experiments are described and images are shown
Cationic double K-hole pre-edge states of CS2 and SF6
Recent advances in X-ray instrumentation have made it possible to measure the
spectra of an essentially unexplored class of electronic states associated
with double inner-shell vacancies. Using the technique of single electron
spectroscopy, spectra of states in CS2 and SF6 with a double hole in the
K-shell and one electron exited to a normally unoccupied orbital have been
obtained. The spectra are interpreted with the aid of a high-level theoretical
model giving excellent agreement with the experiment. The results shed new
light on the important distinction between direct and conjugate shake-up in a
molecular context. In particular, systematic similarities and differences
between pre-edge states near single core holes investigated in X-ray
absorption spectra and the corresponding states near double core holes studied
here are brought out
Carbon dioxide ion dissociations after inner shell excitation and ionization: The origin of site-specific effects
Site-dependent nuclear dynamics in core-excited butadiene
Symmetry breaking and competition between electronic decay and nuclear dynamics are major factors determining whether the memory of the initial core-hole localisation in a molecule is retained long enough to affect fragmentation. We investigate the fate of core holes localised at different sites in the free 1,3 trans butadiene molecule by using synchrotron radiation to selectively excite core electrons from different C 1s sites to π* orbitals. Fragmentation involving bonds localised at the site of the core hole provides clear evidence for preferential bond breaking for a core hole located at the terminal carbon site, while the signature of localisation is weak for a vacancy on the central carbon site. The origin of this difference is attributed to out-of-plane vibrations, and statistical evaporation of protons for vacancies located at the central carbon sites
Multigenerational perspectives on coping with the Holocaust experience: An attachment perspective for understanding the developmental sequelae of trauma across generations
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