We study the strict type assignment for λμ that is presented in [7]. We define a notion of approximants of λμ-terms, show that it generates a semantics, and that for each typeable term there is an approximant that has the same type. We show that this leads to a characterisation via assignable types for all terms that have a head normal form, and to one for all terms that have a normal form, as ...

Seismic imaging for RVSP or drill-bit data recorded for deviated or horizontal wells is a challenging task. Conventional filtering methods such as dip-filtering will fail to separate the primary and multiple (or ghost) reflections because the drill path generates primary and multiple reflections with similar moveout and the same polarity. In this paper, I present a migration method that uses bo...

Accurate identification of depth phases is essential in improving the performance of the event screening process. In the first Release of event screening software, the rules for depth phases were insufficient, in that events that had inappropriate depth phase picks could satisfy the depth phase criteria. To strengthen the depth phase criteria so there is more confidence in the results, a new se...

Perimeter-defense operations, geohazard assessment, and engineering characterization require the detection and localization of subsurface anomalies. Seismic waves incident upon these discontinuities generate a scattered wavefield. We have developed various surface-wave techniques, currently being fielded, that have consistently delivered accurate and precise results across a wide range of surve...

The analytical signal method for seismic attenuation (Q) estimation is reviewed and investigated using a 1D surface data model and field VSP data. The error in Q-factor recovery from modelled data using the analytical signal method is better than 7 percent over a range of Q-factors from 25 to 100. The method is applied to the enhanced downgoing P-wave of an offset VSP-survey from Ross Lake, Sas...

Seismic imaging for RVSP or drill-bit data recorded for deviated or horizontal wells is a challenging task. Conventional filtering methods such as dip-filtering will fail to separate the primary (upgoing) and multiple (downgoing) reflections because the drill path generates primary and multiple reflections with similar moveout and the same polarity. In this paper, I present a new migration meth...

‎let $g$ be a finite group and $nu(g)$ denote the number of conjugacy classes of non-normal subgroups of $g$‎. ‎in this paper‎, ‎all nilpotent groups $g$ with $nu(g)=3$ are classified‎.