We propose a class of graded coronagraphic “amplitude” image masks for high throughput Lyot-type coronagraph that transmits light from an annular region around extended source and suppresses light, with extremely ratio, elsewhere. The interior radius the is comparable its exterior radius. are designed using idea inspired by approach due M. J. Kuchner W. A. Traub (“band-limited” masks) to optima...

A seismic processing workflow based on iterative ray+Born migration/inversion and targetoriented post-processing of the migrated image is developed for fine-scale quantitative characterization of reflectors. The first step of the workflow involves linear iterations of the ray+Born migration/inversion. The output of the first step is a true-amplitude migrated image parameterized by velocity pert...

An average shear-wave velocity structure has been estimated for the path between the Kamchatka Isthmus and Petropavlovsk-Kamchatski. It is obtained from the Monte Carlo inversion of the Rayleigh and Love wave group velocity dispersion curves measured using broad-band seismograms of events in Northern Kamchatka recorded by the IRIS station PET in Petropavlovsk-Kamchatski. The Moho interface was ...

We present an experimental study of the generation of second-harmonic light in a one-dimensional periodic structure truncated by the introduction of a defect in the central period. We observed an enhancement of the nonlinear interaction in the vicinity of the defect when the second-harmonic wave was excited for modes within the forbidden zone or stop band. We also observed an enhancement near t...

TWTs for space applications commonly have a helix pitch profile which incorporates a section with increased phase velocity followed by a negative phase velocity taper. A simple method is described for the initial design of a helix slow-wave structure of this kind to achieve high overall efficiency. It is shown that the use of a section with increased phase velocity increases the beam efficiency...

This research aims to measure four-dimensional, spatio-temporal velocity fields in unsteady periodic flows, such as those around rotorcraft. Periodic planar velocity fields at several slices of the flowfield are used to compute the component normal to the planes. The flow being incompressible, satisfying the continuity equation is sufficient. The velocity field reconstruction technique is valid...