Absorption and transport of water in porous stone materials is an important issue, since it is often related to the durability and deterioration of the material. Traditional standardized tests are aimed to determine the rate of absorption or water-permeability by measuring the weight or volume of absorbed water through a given surface area with time. Nevertheless, in situations like wetting of stone or brick walls not only the quantity of the absorption is important, but also the maximum height and velocity of the water-front elevation should be considered. In present paper the relationship between the velocity of capillary elevation and height of capillary elevation is studied. The aim of the analysis was to find an equation which characterizes the measured absorption process adequately. Three types of power functions were used to approximate the velocity of the water-front elevation. These approximating functions were computed for 13 measurements made with porous limestone, and the accuracy of the approximations was evaluated. It was found, that equations in the form of v (h) = c/h + d can be fitted to the measured data with high accuracy, and the possible range of the c coefficient was determined for porous limestone.

Abstract. We introduce a new method to approximate algebraic space curves. The algorithm combines a subdivision technique with local approximation of piecewise regular algebraic curve segments. The local technique computes pairs of polynomials with modified Taylor expansions and generates approximating circular arcs. We analyze the connection between the generated approximating arcs and the osculating circles of the algebraic curve.

Abstract. We present an algorithm generating a collection of fat arcs which bound the zero set of a given bivariate polynomial in BernsteinBézier representation. We demonstrate the performance of the algorithm (in particular the convergence rate) and we apply the results to the computation of intersection curves between implicitly defined algebraic surfaces and rational parametric surfaces.

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