The one-dimensional Schrodinger equation is considered when the potential and its rst moment are absolutely integrable. The transmission coe cient vanishes at zero energy in the generic case, and it never vanishes in the exceptional case. It is shown that any nontrivial exceptional potential can always be fragmented into two generic potentials. Furthermore, any nontrivial potential, generic or...

The problem of information “getting into the wrong hands” has existed since the first stored data computer systems. Numerous companies and government departments have been embarrassed by data left on un-erased media such as magnetic tape and discovered by inquiring minds. The advent of data communications brought the problem to a whole new level, since information could be transmitted over long...

This paper investigates the processing of conditional sentences and sentences with ‘since’ in two respects. Firstly, we investigate the clausal implicature originating from the scale . Secondly, we investigate how modals can affect the interpretation of these sentences. A reading time experiment is reported which involved these two factors. It appears that ‘since’ is pr...

We apply the CIP (Cubic Interpolated Profile) scheme to the numerical simulation of the acoustic wave propagation based on characteristic equations.The CIP scheme is based on a concept that both the wavefield and its spatial derivative propagate along the same characteristic curves derived from a hyperbolic differential equation. We describe the derivation of the characteristic equations for th...

Abstract When a monochromatic wavefield is focused, its phase, compared to that of a non-diffracted spherical wave, undergoes a rapid π phase change. This effect bears the name of its discoverer, L.G. Gouy. In a partially coherent wavefield the phase is a random quantity and therefore, when such a field is focused, its Gouy phase is undefined. However, the phase of the correlation functions tha...

S U M M A R Y Acoustic wavefields produced using sources appropriately delayed in time can be focused at known positions and times in a heterogeneous medium. Seismoelectric conversion occurs if the acoustic focus point coincides with a discontinuity in electrical and hydrological medium properties, thus generating a current density. The current generates a potential difference, which can be obs...

In seismic data processing, we often need to interpolate and extrapolate data at missing spatial locations. The reconstruction problem can be posed as an inverse problem where, from inadequate and incomplete data, we attempt to reconstruct the seismic wavefield at locations where measurements were not acquired. We propose a wavefield reconstruction scheme for spatially band-limited signals. The...

Wave-equation migration using one-way wavefield extrapolation operators is commonly used in industry to generate images of complex geologic structure from 3D seismic data. By design, most conventional wave-equation approaches restrict propagation to downward continuation, where wavefields are recursively extrapolated to depth on Cartesian meshes. In practice, this approach is limited in high-an...