Proving the equivalence of successive, closely related versions of a program has the potential of being easier in practice than functional verification, although both problems are undecidable. There are three main reasons for this claim: 1) it circumvents the problem of specifying what the program should do, 2) the problem can be naturally decomposed and hence is computationally easier, and 3) ...

Anewmethod that combines radar reflectivities from individualNextGenerationWeatherRadars (NEXRAD) into a three-dimensional composite with high horizontal and vertical resolution is used to estimate storm-top altitudes for the continental United States east of the RockyMountains. Echo-top altitudes are compared with the altitude of the lapse-rate tropopause calculated from the ERA-Interim reanal...

The NE2001 model for the free electron distribution of the Milky Way includes ad hoc electron “clumps” to reconcile line of sight observables with basic model predictions (Cordes et al. 2002). While MAGPIS (Multi-Array Galactic Plane Imaging Survey) is insensitive to emission from individual diffuse HII regions (ne ∼10 cm), by investigating the 20 cm maps we are able to verify their assumption ...

Information technology today is a complex area, in which new problems and challenges constantly arise and innovations emerge. The ability to incorporate an innovation in time or to solve a problem efficiently can mean competitive advantages for some firms. Being responsive in IT involves being alert, knowledgeable and prepared to face technical problems and to solve them in appropriate ways. In...

We define the notion of a weakly pointed tree, and characterize the amount of genericity necessary to prevent a uniformly branching tree being weakly pointed. We use these ideas to show there is no topological analogue of a measure-theoretic selection theorem of Graf and Mauldin. We consider some topological and recursion-theoretic questions motivated by the following measure-theoretic result o...