Pulsed-field-gradient NMR techniques are demonstrated for measurements of time-dependent gas diffusion. The standard PGSE technique and variants, applied to a free gas mixture of thermally polarized xenon and O2, are found to provide a reproducible measure of the xenon diffusion coefficient (5.71 x 10(-6) m2 s-1 for 1 atm of pure xenon), in excellent agreement with previous, non-NMR measurement...

We present useful expressions predicting the filling time of gaseous species inside photonic crystal fibers. Based on the theory of diffusion, this gas-filling model can be applied to any given fiber geometry or length by calculating diffusion coefficients. This was experimentally validated by monitoring the filling process of acetylene gas in several fiber samples of various geometries and len...

This paper presents helpful expressions predicting the filling time of gaseous species inside photonic crystal fibres. Based on the theory of diffusion, our gas-filling model can be applied to any given fibre geometry or length by calculating diffusion coefficients. This was experimentally validated by monitoring the filling process of acetylene gas in several fibre samples of various geometrie...

We study gas diffusion through computer-generated random fibre networks using random walk simulations. The simulation results are consistent with steady-state experiments. The comparison of the simulated time-dependent diffusion flux with one-dimensional diffusion theory suggests that the latter is invalid at low porosities and low thicknesses. We also find that, if sorption is relevant, steady...

Gas mixing in a T-shape micro mixer has been simulated using the Direct Simulation Monte Carlo (DSMC) method. It is considered that the adequate mixing occurs when the mass composition of the species, CO or N2, deviates below 1 % from their equilibrium composition. The mixing coefficient is defined as the ratio of the mixing length to the main channel’s height. As the inlet Kn increases, while ...

Diffusion of CO2 inside leaves is generally regarded to be from the substomatal cavities to the assimilating tissues, i.e. in the vertical direction of the leaf blades. However, lateral gas diffusion within intercellular air spaces may be much more effective than hitherto considered. In a previous work it was demonstrated that, when 'clamp-on' leaf chambers are used, leaf internal 'CO2 leakage'...

gas mixing in a t-shape micro mixer has been simulated using the direct simulation monte carlo (dsmc) method. it is considered that the adequate mixing occurs when the mass composition of the species, co or n2, deviates below 1 % from their equilibrium composition. the mixing coefficient is defined as the ratio of the mixing length to the main channel’s height. as the inlet kn increases, while ...

Gas transport mechanisms that characterize the hermetic behavior of MEMS packages are fundamentally different depending upon which sealing materials are used in the packages. In metallic seals, gas transport occurs through a few nanoscale leak channels (gas conduction) that are produced randomly during the solder reflow process, while gas transport in polymeric seals occurs through the bulk mat...