In a first-order reversed-phi motion stimulus (Anstis, 1970), the black-white contrast of successive frames is reversed, and the direction of apparent motion may, under some conditions, appear to be reversed. It is demonstrated here that, for many classes of stimuli, this reversal is a mathematical property of the stimuli themselves, and the real problem is in perceiving forward motion, which i...

This article describes a new method for attempting to solve Sokoban puzzles by means of an efficient algorithm, a task which has proven to be extremely difficult because of both the huge search tree depth and the large branching factor. We present a way of solving Sokoban puzzles that, using several heuristics, starts from the final state of a puzzle, and from there works its way back to the in...

In the usual formulation of the Kirchhoff diffraction integral, a scalar field with harmonic time dependence at frequency ω is deduced at the interior of a charge-free volume from knowledge of the field (or its normal derivative) on the bounding surface. In particular, the field is propagated forwards in time from the boundary to the desired observation point. Construct a time-reversed version ...

We examine words w satisfying the following property: if x is a subword of w and |x| is at least k for some fixed k, then the reversal of x is not a subword of w.

1. Universidade Federal Fluminense, Niterói (RJ) Brasil. 2. Universidade Federal do Rio de Janeiro, Rio de Janeiro (RJ) Brasil. 3. Faculdade de Medicina de Petrópolis, Petrópolis (RJ) Brasil. 4. Santa Casa de Misericórdia de Porto Alegre, Porto Alegre (RS) Brasil. 5. Universidade Federal de Ciências da Saúde de Porto Alegre, Porto Alegre (RS) Brasil. A 35-year-old man presented to the emergency...

The aim of this paper is to introduce the time reversed absorbing conditions (TRAC) in time reversal methods. These new boundary conditions enable one to “recreate the past” without knowing the source which has emitted the signals that are back-propagated. This new method does not rely on any a priori knowledge of the physical properties of the inclusion. We prove an energy estimate for the res...

There is mounting evidence that there are three parallel streams of visual motion computation—firstand second-order systems that are primarily monocular and a third-order binocular system (Lu & Sperling, 1995a, 1995b, 1996c). The first-order system extracts motion from drifting luminance modulations, and the secondorder system extracts motion from drifting texture contrast modulations. These pr...

Appearance: The reversed halo sign (also known as the atoll sign, reverse halo sign, and the fairy ring sign) is defined by central ground-glass opacity with a surrounding halo or crescent of consolidation (Fig. 1). This should not be confused with the halo sign which refers to central consolidation with a surrounding halo or rim of ground-glass opacity. Furthermore, the reversed halo sign shou...