A Framework for Surface Modification by Electrical Discharge Coating using Variable Density Electrodes

Surface modification is the process of altering physical or chemical characteristics of the work-piece surface. In this paper, various surface modification techniques have been discussed. One of the most appropriate surface modification technique is electrical discharge coating (EDC), in which the hard material is made to deposit onto the work-piece in a state of reverse polarity condition. Different mechanisms of carrying out EDC are presented. Deliberate material transfer takes place by using electrodes or by dispersant of metal powders into the di-electric. A detailed review of the literature on the theme of surface modification through the EDC has been conducted. In last, a framework for conducting surface modification by EDC employing using density electrodes of same material is presented.

Isoluminant Colour Contrast Does Not Fill in Surfaces

It has been suggested (Livingstone and Hubel, 1988 Science240 740 – 749) that the ‘colour-blind’ magnocellular pathways generate the neurophysiological basis of surfaces with illusory contours since the latter do not seem to be perceived in inducing configurations of a given colour which is isoluminant with regard to the colour of the background (equiluminant colour contrast). However, psychophysical data allowing us to assess the relative visibility of illusory surfaces in coloured stimuli with luminance contrast compared to configurations with equiluminant colour contrast are not yet available. We designed a colour-matching experiment where ten naive observers had to adjust the intensity of a red illusory surface so that it appeared to match the intensity of the red background. The configurations used were Kanizsa squares with green inducing elements, isoluminant or not with regard to the background. Isoluminance was assessed individually for each observer by means of a classical flicker test. A brightness-matching procedure was applied to configurations of achromatic inducers on a grey background. In this case, the inducers had either all the same contrast polarity (light), or both polarities (light and dark) within a given configuration. Luminance contrast in the achromatic configuration with only one polarity was the same as in the non-isoluminant colour condition. Luminance contrasts of light and dark inducers in the mixed-polarity condition were physically balanced. The results show that the mean point of subjective equality (PSE) of the test surface corresponds to the physical intensity of the background with equiluminant colour contrast only, indicating the absence of an apparent surface in this condition. This result supports the idea that magnocellular pathways in the human visual system mediate the neurophysiological genesis of illusory surfaces. In all the other stimulus conditions, the PSE does not correspond to the physical intensity of the background. Matching ‘errors’ are significantly stronger in the achromatic conditions, but, paradoxically, strongest in the condition with balanced contrasts of opposite polarity. This finding suggests that luminance contrast is not the only determinant of the perceived strength of illusory surfaces.