Examples of transport processes include heat conduction ( energy transfer ), fluid flow ( momentum transfer ), molecular diffusion ( mass transfer ), radiation and electric charge transfer in semiconductors.
22.
If we consider an inert species ( no reaction ) with no sources and assume molecular diffusion to be negligible, only the advection terms on the left hand side of the equation survive.
23.
"' Molecular diffusion "', often simply called "'diffusion "', is the thermal motion of all ( liquid or gas ) particles at temperatures above absolute zero.
24.
Similar to the Kolmogorov microscales, which describe the smallest scales of turbulence before viscosity dominates; the Batchelor scale describes the smallest length scales of fluctuations in scalar concentration that can exist before being dominated by molecular diffusion.
25.
Once a roughly-held-together object called a " green body " is made, it is baked in a kiln, where atomic and molecular diffusion processes give rise to significant changes in the primary microstructural features.
26.
Once the concentrations are equal the molecules continue to move, but since there is no concentration gradient the process of molecular diffusion has ceased and is instead governed by the process of self-diffusion, originating from the random motion of the molecules.
27.
"' Diffusivity "'or "'diffusion coefficient "'is a proportionality constant between the molar flux due to molecular diffusion and the gradient in the concentration of the species ( or the driving force for diffusion ).
28.
Using a fluid bromide tracer, Dicke ( in Graf 1992 ) found molecular diffusion alone to penetrate soft sediments to 4 cm in one day and 8 cm after 4 days . Bioturbation can accelerate this process by up to a factor of ten.
29.
As a result, internal diabatic heating / cooling due to molecular diffusion explains why laboratory experiments show evidence of circulations developing as the result of surface heating / cooling ( Park and Whitehead, 2000 ) or even when the heating is above the cooling ( Coman et al ., 2006 ).
30.
Where f _ \ mathrm { IVIM } is the volume fraction of incoherently flowing blood in the tissue ( flowing vascular volume ), F _ \ text { perf } the signal attenuation from the IVIM effect and F _ \ text { diff } is the signal attenuation from molecular diffusion in the tissue.
