Adaptive isogeometric analysis for phase‐field modeling of anisotropic brittle fracture

The surface energy a phase‐field approach to brittle fracture in anisotropic materials is also anisotropic and gives rise to second‐order gradients in the phase field entering the energy functional. This necessitates C 1 continuity of the basis functions which are used to interpolate the phase field. The basis functions which are employed in isogeometric analysis (IGA), such as nonuniform rational B‐splines and T‐splines naturally possess a higher order continuity and are therefore ideally suited for phase‐field models which are equipped with an anisotropic surface energy. Moreover, the high accuracy of spline discretizations, also relative to their computational demand, significantly reduces the fineness of the required discretization. This holds a fortiori if adaptivity is included. Herein, we present two adaptive refinement schemes in IGA, namely, adaptive local refinement and adaptive hierarchical refinement, for phase‐field simulations of anisotropic brittle fracture. The refinement is carried out using a subdivision operator and exploits the Bézier extraction operator. Illustrative examples are included, which show that the method can simulate highly complex crack patterns such as zigzag crack propagation. An excellent agreement is obtained between the solutions from global refinement and adaptive refinement, with a reasonable reduction of the computational effort when using adaptivity

A particle event at 5 AU and 20° southern latitude from measurements with the EPAC instrument on Ulysses

In November 1992, the Ulysses spacecraft observed a multiple solar particle event and a CME event at 5.2 AU and a heliographic latitude of 20° S which were superimposed to the recurrent corotating interacting region. Distinct particle flux increases caused by these events were observed in all energy channels of the EPAC experiment. The experimental findings are discussed. © 1995 Kluwer Academic Publishers

Perceptions of forest experts on climate change and fire management in European Mediterranean forests

Climate change has already increased fire risk in Mediterranean forests. Adaptation options related to forest fires and climate change include measures related to fuel management, fire fighting and infrastructure, as well as public awareness. The importance of each of these measures was evaluated in six Mediterranean countries in a study initiated within the COST Action FP0703 "Expected Climate Change and Options for European Silviculture". A questionnaire survey was used to document the views of foresters and forest scientists. Country differences were observed and adaptation measures related to fire fighting efficiency and public awareness were valued as more important than fuel management. Results were discussed in the light of a critical review of adaptive fire management measures with special reference to European Mediterranean countries. © SISEF