In this paper, a method for measuring the instantaneous shear-stress distribution over a solid surface in a fluid flow is studied by using a surface-flow visualization technique with a shear-sensitive liquid-crystal coating. The colour response of the liquid-crystal coating is calibrated against the various shear-stress magnitudes and directions with an experimental test section of laminar channel flow. The measurement of instantaneous shear-stress distribution is carried out using two colour CCD cameras, which are situated side by side in stereoscopic arrangement. The colour-to-shear-stress transformation is conducted by analysing the hue distribution of the visualized colour image with the calibrated relationships between the hues from the two colour CCD cameras and the shear-stress magnitude and direction. The usefulness of this technique was demonstrated by the measurement of shear-stress distribution around a circular cylinder on a surface under decelerating flow conditions.

The purpose of this study was to evaluate the effectiveness of resin coating as a means of preventing marginal leakage beneath full cast crowns which were emplaced using different cements. Standard full cast crown preparation was made on 64 extracted premolars.These samples were then divided into four groups, with half of each group coated with dentin coating material after preparation.Crowns were cemented onto the teeth using zinc cement, Fuji I, Vitremer, or C&B Metabond. The samples were thermal-cycled for 10,000 cycles. They were then immersed in erythrosine solution, sectioned, and observed under a microscope.Microleakage analyses were performed using a 0-4 point system. The data were statistically analyzed. There were significant differences between the coated specimens and the uncoated specimens using Fuji I and Vitremer.The results showed that a resin coating could decrease the amount of marginal leakage when applied with these two cemPntfi_