Plane micropolar elasticity with surface flexural resistance

We propose a linear surface/interface model for plane deformations of a micropolar elastic solid based on a higher-order surface elasticity theory capable of incorporating bending and twisting effects. The surface/interface is modeled as a bending-resistant Kirchhoff micropolar thin shell perfectly bonded to the boundary of the solid. It is anticipated that by combining micropolar bulk and surface effects in this way, the enhanced model will most accurately capture the essential characteristics (in particular, size dependency) required in the modeling of materials with significant microstructure as well as in the modeling of classes of nanomaterials. The corresponding boundary value problems are particularly interesting in that they involve boundary conditions of order higher than that of the governing field equations. We illustrate our theory by analyzing the simple problem of a circular hole in a micropolar sheet noting, in particular, the extent to which surface effects and micropolar properties each contribute to the deformation of the sheet.     

The complexity of the graph access structures on six participants

In this paper, we deal with determining the exact values for the complexity of the five graph access structures on six participants, which remained as open problems in van Dijk’s paper (Des Codes Cryptogr 6:143–169, 1995). We prove that the complexity for each of the five graph access structures is equal to 7/4.