A dynamic gradient ratio test apparatus

The soil-geotextile filtration mechanism is a complex process which depends on physical compatibility between the geotextile and the soil to be retained. Several methods have been proposed by researchers for assessing the filtration behaviour of soil-geotextile composite systems under steady state conditions. The Gradient Ratio (GR) test is the most commonly used method for measuring filtration compatibility of soil-geotextile systems. This paper describes the design of a modified GR permeability test apparatus to overcome disadvantages associated with traditional GR test devices. The apparatus can perform filtration tests under static and dynamic conditions and can be used to evaluate the filtration compatibility of fine-grained soils with geotextiles. The apparatus is incorporated within a triaxial testing system, hence representative field stress conditions can be applied to test specimens. Some exemplar GR tests performed on coarse and fine-grained soils with a non-woven geotextile are presented in this paper. Unidirectional dynamic loads are applied within the filtration tests to replicate highway traffic loading. Test results show that dynamic loading affects the filtration behaviour at the soil-geotextile interface by increasing the fine particles migration towards the geotextile, but that, for the soil evaluated here, this effect was small

Faceting at the Silicon (100) Crystal-Melt Interface: Theory and Experiment

Molecular-dynamics simulations and in situ experimental observations of the melting and equilibrium structure of the crystalline Si(100)-melt interface are described. The equilibrium interface is structured, exhibiting facets established on (111) planes

Simple model of adsorption on external surface of carbon nanotubes: a new analytical approach basing on molecular simulation data

Nitrogen adsorption on carbon nanotubes is wide- ly studied because nitrogen adsorption isotherm measurement is a standard method applied for porosity characterization. A further reason is that carbon nanotubes are potential adsorbents for separation of nitrogen from oxygen in air. The study presented here describes the results of GCMC simulations of nitrogen (three site model) adsorption on single and multi walled closed nanotubes. The results obtained are described by a new adsorption isotherm model proposed in this study. The model can be treated as the tube analogue of the GAB isotherm taking into account the lateral adsorbate-adsorbate interactions. We show that the model describes the simulated data satisfactorily. Next this new approach is applied for a description of experimental data measured on different commercially available (and characterized using HRTEM) carbon nanotubes. We show that generally a quite good fit is observed and therefore it is suggested that the observed mechanism of adsorption in the studied materials is mainly determined by adsorption on tubes separated at large distances, so the tubes behave almost independently