Sectional-Curvature Preserving Skinning Surfaces with a 3D Spine Curve

. This work deals with the problem of constructing sectional-curvature preserving (scp) C 2 -continuous surfaces, which interpolate point-sets lying on planes perpendicular to a three-dimensional spine curve. The proposed method of solution employs skinning surfaces, whose skeletal lines and blending functions belong to a special family of polynomial splines of non-uniform degree, already used for shape-preserving curve interpolation in the plane (see [4], [5]) as well as space (see [3]). Using an appropriate affine transformation, the problem simplifies to a sectional-curvature preservation problem with a straight line as spine curve, a case thoroughly studied in [2]. x1. Introduction Developing automatic algorithms for shape-preserving curve and surface interpolation, is a CAGD domain with intensive basic-research activity and a steadily increasing audience in the CAD/CAM community. While the planar problem is well studied (see [5] and the references cited therein), it seems that..

Authigenic carbonate mineral formation in the Pagassitikos palaeolake during the latest Pleistocene, central Greece

The Pagassitikos Gulf in Greece is a semi-enclosed bay with a maximum depth of 102 m. According to the present-day bathymetric configuration and the sea level during the latest Pleistocene, the gulf would have been isolated from the open sea, forming a palaeolake since ~32 cal. ka b.p. Sediment core B-4 was recovered from the deepest sector of the gulf and revealed evidence of a totally different depositional environment in the lowest part of the core: this contained light grey-coloured sediments, contrasting strongly with overlying olive grey muds. Multi-proxy analyses showed the predominance of carbonate minerals (aragonite, dolomite and calcite) and gypsum in the lowest part of the core. Carbonate mineral deposition can be attributed to autochthonous precipitation that took place in a saline palaeolake with high evaporation rates during the last glacial–early deglacial period; the lowest core sample to be AMS 14C dated provided an age of 19.53 cal. ka b.p. The palaeolake was presumably reconnected to the open sea at ~13.2 cal. ka b.p. during the last sea-level rise, marking the commencement of marine sedimentation characterised by the predominance of terrigenous aluminosilicates and fairly constant depositional conditions lasting up to the present day