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In this letter, we report an energetics-based model to explain the self-organizing nanomesa and nanowell patterns recently observed in Langmuir-Blodgett (LB) films of polyvinylidene fluoride trifluoroethylene [P(VDF-TrFE)] copolymers. The feature size of nanomesas and nanowells has been estimated using a linear stability analysis, and the morphology of the nanomesas and nanowells has been revealed by the numerical simulation, both in good agreement with experiments. A number of other model predictions regarding the nanomesa and nanowell formation also agree with experimental observations. The model can be used to guide the design and optimization of nanostructures in the P(VDF-TrFE) LB films and possibly in other thin polymer films.

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In the village of Donghekou (in Qingchuan County, Sichuan Province, China), a major landslide was triggered by the Wenchuan earthquake in 2008 with more than 10 9 10 6 m 3 of rock displaced. The kinematic behavior of this landslide is simulated using a 2D discrete element model. The numerical model used in this work is composed of discs bonded together. The initial boundary conditions are applied along the ball-wall contacts by using an initial velocity estimated from the strong motion data. The constraints are mainly issued from the final geometry of the landslide including its capacity to dam the river. The modeling thus indicates that a low friction coefficient (about 0.1) is required to account for the actual landslide characteristics. The runout behaviors are analyzed and some useful conclusions are drawn.