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Dispersion is a process by which (in the case of solid dispersing in a liquid) agglomerated particles are separated from each other, and a new interface between the inner surface of the liquid dispersion medium and the surface of the dispersed particles is generated. This process is facilitated by molecular diffusion and convection. [4]
In materials science, dispersion is the fraction of atoms of a material exposed to the surface. In general, D = N S / N , where D is the dispersion, N S is the number of surface atoms and N T is the total number of atoms of the material. [ 1 ]
Many atmospheric dispersion models are referred to as boundary layer models because they mainly model air pollutant dispersion within the ABL. To avoid confusion, models referred to as mesoscale models have dispersion modeling capabilities that extend horizontally up to a few hundred kilometres. It does not mean that they model dispersion in ...
UDM – Urban dispersion model is a Gaussian puff based model for predicting the dispersion of atmospheric pollutants in the range of 10m to 25 km throughout the urban environment. It is developed by the Defense Science and Technology Laboratory for the UK Ministry of Defence. It handles instantaneous, continuous, and pool releases, and can ...
Natural organic matter produced by the decomposition of plants and wood debris in soils (humic substances) also has a pronounced polydispersed character. It is the case of humic acids and fulvic acids, natural polyelectrolyte substances having respectively higher and lower molecular weights.
Diffusion is of fundamental importance in many disciplines of physics, chemistry, and biology. Some example applications of diffusion: Sintering to produce solid materials (powder metallurgy, production of ceramics) Chemical reactor design; Catalyst design in chemical industry; Steel can be diffused (e.g., with carbon or nitrogen) to modify its ...
The laminar finite rate model computes the chemical source terms using the Arrhenius expressions and ignores turbulence fluctuations. This model provides with the exact solution for laminar flames but gives inaccurate solution for turbulent flames, in which turbulence highly affects the chemistry reaction rates, due to highly non-linear Arrhenius chemical kinetics.
Fick's first law relates the diffusive flux to the gradient of the concentration. It postulates that the flux goes from regions of high concentration to regions of low concentration, with a magnitude that is proportional to the concentration gradient (spatial derivative), or in simplistic terms the concept that a solute will move from a region of high concentration to a region of low ...