This paper is intended to provide a mathematical model about mass transfer of natural medicinal components in production process of andrographolide as a medical plant. An inverse problem that included a partial differential equation in conjunction with initial and boundary conditions is introduced to estimate diffusivity of andrographolide during production of solvent extraction. To solve the i...

Radial electron heat transport in low collisionality, magnetically-confined toroidal plasmas is shown to result from paleoclassical Coulomb collision processes (parallel electron heat conduction and magnetic field diffusion). In such plasmas the electron temperature is equilibrated along magnetic field lines a long length L (>> periodicity length πR0q), which is the minimum of the electron coll...

high moisture levels in fresh dairy manure provide a suitable environment for growth of pathogens and cause environmental pollution. dry manure can be used for different purposes in agriculture and in livestock industry. such heat properties of manure as specific heat, thermal conductivity and thermal diffusivity are important needed factors for the design and development of a suitable efficien...

Hyperpolarized (3)He gas MRI was used to form maps of the effective diffusivity of gas in human lungs. Images of diffusion as well as spin density are presented from a study of 11 healthy volunteers and 5 patients with severe emphysema. The effective rate of diffusion, D(e), of the gas is reduced by the alveolar walls; tissue destruction in emphysema is hypothesized to result in larger D(e). In...

Near-surface “effective diffusivities” associated with geostrophic eddies in the Southern Ocean are estimated by numerically monitoring the lengthening of idealized tracer contours as they are strained by surface geostrophic flow observed by satellite altimetry. The resulting surface diffusivities show considerable spatial variability and are large (2000 m s ) on the equatorward flank of the An...

We study the problem of homogenization for inertial particles moving in a time dependent random velocity field and subject to molecular diffusion. We show that, under appropriate assumptions on the velocity field, the large–scale, long–time behavior of the inertial particles is governed by an effective diffusion equation for the position variable alone. This is achieved by the use of a formal m...

A major aspect of describing transport in heterogeneous media has been that of relating effective diffusivities to the topological properties of the medium. While such effective transport coefficients may be useful for mass fractals or under steady state conditions, they are not adequate under transient conditions for self-similar pore fractal media. In porous formations without scale, diffusio...

The formation–distribution of condensed water in diffusion medium of proton exchange membrane fuel cells, and its tendency to reduce the local effective mass diffusivity and to influence cell performance, are studied. First the local effective mass diffusivity of a fibrous diffusion medium is determined as a function of the local porosity and local water saturation, using the network model for ...