introduction: preferential flow is one of the major processes influencing the rapid movement of pollutants to ground water.  macropores created by plant roots provide pathways for rapid transport of pollutants in a soil profile. the growth of plant roots into soil causes creation of big pores that improve water movement and solute transport through soil profile. field soils or undisturbed soils...

[1] A physically based description is provided for the transverse dispersion coefficient in porous media as a function of Péclet number, Pe. We represent the porous medium as lattices of bonds with square cross section whose radius distribution is the same as computed for Berea sandstone and describe flow (Stokes equation) and diffusion (random walk method) at the pore scale ( mm) to compute th...

The common and traditional method for dispersion compensation in optical domain is concatenating the transmit optical fiber by a compensating optical fiber having high-negative dispersion coefficient. In this paper, we take an opposite direction and show how an optical fiber with high-positive dispersion coefficient can also be used for dispersion compensation. Our optical dispersion compensati...

The purpose of this work was to investigate the effect of solute size on diffusive-dispersive transport in porous media. Miscible displacement experiments were performed with tracers of various sizes (i.e. tritiated water (3H20), pentafluorobenzoate (PFBA), and 2,4-dichlorophenoxyacetic acid (2,4-D)) and a homogeneous, nonreactive sand for pore-water velocities varying by three orders of magnit...

Chromatic dispersion profile of dual-concentric-core photonic crystal fibers is optimized for broadband dispersion compensation of single mode fibers (SMFs) by using genetic algorithm incorporated with full-vector finite-element method. From the numerical results presented here, it is found that by increasing the distance between central core and outer ring core, larger negative dispersion coef...

Rare sugars are becoming increasingly interesting for many industrial applications, due to properties such as low energy content and potential pharmaceutical uses. D-psicose is one of the rare sugars with a future use as a sweetener and precursor for pharmaceuticals. It can be enzymatically produced from a cheap substrate, Dfructose. Because of the position of the thermodynamic equilibrium the ...

B = dimensionless coefficient in polynominals b = dimensionless coefficient in polynominals F = dimensionless radial velocity G = dimensionless tangential velocity H = dimensionless axial velocity K = 7 / 2 p r ~ ( v u ) ' / ~ , dimensionless parameter Q = $ow rate 8' = dimensionless flow rate r = radial coordinate u = radial velocity II = tangential velocity w = axial velocity z = axial coordi...