abstract the concept of armouring is used to discuss the coarse surface layer in rivers. selective erosion in an alluvial channel reach for which there is no upstream sediment supply can lead to formation of a layer coarser than the under laying material. this phenomenon inhibits sediment transport from the reach.numerical modeling of armouring river bed, provides an approach to simulation of t...

High temperature nanoindentation experiments are conducted to assess the activation enthalpy for deformation of nanocrystalline Ni-W alloys, for grain sizes between 3 and 80 nm. Thermal softening becomes less pronounced at finer grain sizes, and the activation enthalpy has an apparent inflection at a grain size near ~10-20 nm, in the vicinity the Hall-Petch breakdown. This inflection is related...

Magnetic small-angle neutron scattering experiments were performed on nanostructured Fe, Co and Ni samples of varying grain size, produced by inert-gas condensation. The experiments show that the spontaneous spatial magnetic correlations forming in zero-field extend over many individual grains. These correlations depend strongly on grain size. In Fe, they have a minimum at a grain size of aroun...

Exploration of optical properties of organic crystalline semiconductors thin films is challenging due to submicron grain sizes and the presence of numerous structural defects, disorder and grain boundaries. Here we report on the results of combined linear dichroism (LD)/ polarization-resolved photoluminescence (PL) scanning microscopy experiments that simultaneously probe the excitonic radiativ...

This study links two models, one that simulates changes in snow microstructure and one that recovers microstructure properties from measurements of snow reflectance. An energy and mass transfer model, SNTHERM.89, was used to calculate snow grain growth. Grain-sizes from the model and measurements of grain bond areas provided estimates of the surface-to-volume ratio of the bulk snow, which were ...

Nanocrystalline metals, i.e. metals with grain sizes from 5 to 50 nm, display technologically interesting properties, such as dramatically increased hardness, increasing with decreasing grain size. Due to the small grain size, direct atomic-scale simulations of plastic deformation of these materials are possible, as such a polycrystalline system can be modeled with the computational resources a...

[1] EL chondrites exhibit larger average metal grain sizes than EH chondrites, a difference attributed by Easton [1983] to metamorphic coarsening, as most EL chondrites are equilibrated, and most EH chondrites are unequilibrated. In this paper, we present metal grain size data for three unequilbrated EL3 chondrites (PCA 91020; ALH 85119; MAC 88180) , and three EH3 chondrites (ALH 84170; PCA 910...