When a monochromatic electromagnetic plane wave is incident on an infinitely extending surface with the translation invariance property, a curious phenomenon often takes place at a low grazing angle of incidence, at which the total wave field vanishes and a dark shadow appears. This paper looks for physical and mathematical reasons why such a shadow occurs. Three cases are considered: wave refl...

The oblique spike or contrast edge seen by an off-summit observer on a mountain shadow when the sun is low is shown to be a perspective effect that depends on the observer's position within the shadow. The degree of visibility of the shadow is due to contrast effects between differently illuminated aerosols. Numerical simulations are used to demonstrate these points.

In this paper we present an image-based algorithm to render visually plausible anti-aliased soft shadows in real time. Our technique employs a new shadow pre-filtering method based on an extended exponential shadow mapping theory. The algorithm achieves faithful contact shadows by adopting an optimal approximation to exponential shadow reconstruction function. Benefiting from a novel overflow f...

An undo facility is an essential component of most interactive applications. In current operating system shells, whether textual or graphical, such facilities are typically very poor. Algorithms are presented for adding a recovery mechanism to a shell which allows previous commands to be selectively undone and redone, and previous versions of files to be recovered. The recovery mechanism involv...

Shadows provide the human visual system with important cues to sense spatial relationships in the environment we live in. As such they are an indispensable part of realistic computer-generated imagery. Unfortunately, visibility determination is computationally expensive. Image-based simplifications to the problem such as Shadow Maps perform well with increased scene complexity but produce artif...

In this paper we propose several methods that can greatly improve image quality when using the shadow mapping algorithm. Shadow artifacts introduced by shadow mapping are mainly due to low resolution shadow maps and/or the limited numerical precision used when performing the shadow test. These problems especially arise when the light source’s viewing frustum, from which the shadow map is genera...

In this paper we show how to improve the detection of shadows in natural scenes using a novel combination of colour and illumination features. Detecting shadows is useful because they provide information about both light sources and the shapes of objects thereby illuminated. Recent shadow detection methods use supervised machine learning techniques with input from colour and texture features ex...

introduction: low-frequency stimulation (lfs) has a delaying effect on kindled seizures acquisition. in the present study we examined the role of galanin receptors in the inhibitory effects of lfs on kindled seizures induced by electrical stimulation of perforant path. methods: animals were stimulated daily at the ad threshold intensity with a rapid kindling procedure. lfs was applied immediate...

conclusions no interactivity is present in modulatory effects of gabaa receptors and elf-emfs on serum testosterone of male rats. patients and methods fifty adult male rats were randomly assigned into 10 groups. groups 2, 4, 6, 8, and 10 were exposed to elf-emf for 30 days 8hrs per day; while, the remaining groups (1, 3, 5, 7, and 9) were sham exposed animals. at the end of the experiment, anim...

introduction: application of low-frequency stimulation (lfs) is a new method for treatment of drug resistant epileptic patients. previous studies demonstrated that activation of receptors coupled to gi proteins is one of the mechanisms of the anticonvulsant effect of lfs. thus, in this study, alterations in the expression of rgs4 and rgs10 proteins, as negative regulators of gi proteins, were i...