diffusivity's Usage Examples:

The diffusivity can be deduced from observations at different depths x' and x", by observing the ratio of the amplitudes, which is (x '- x ") for a simple-harmonic wave.

Excluding these exceptional cases, however, the variations of the diffusivity appeared to follow the variations of the seasons with considerable regularity in successive years.

On some occasions, owing to the sudden melting of a surface layer of ice and snow, a large quantity of cold water, percolating rapidly, gave for a short time values of the diffusivity as high as.

For the particular soil in question it was found that the diffusivity varied enormously with the degree of moisture, falling as low as ooio C.G.S.

We thus obtain the simple equation k'(de'/dx') - k"(de"/dx") =c (area between curves)/(T - T'), (4) by means of which the average value of the diffusivity klc can be found for any convenient interval of time, at different seasons of the year, in different states of the soil.

The method of deducing the diffusivity from these curves is as follows: - The total quantity of heat absorbed by the soil per unit area of surface between any two dates, and any two depths, x' and x", is equal to c times the area included between the corresponding curves.

No calorimetric observations are required, but the results are obtained in terms of the thermal capacity of unit volume c, and the measurements give the diffusivity klc, instead of the calorimetric conductivity k.

The velocity of propagation of temperature waves will be the same under similar conditions in two substances which possess the same diffusivity, although they may differ in conductivity.

If Q is expressed in terms of this unit in equation (I), it is necessary to divide by c, or to replace k on the right-hand side by the ratio k/c. This ratio determines the rate of diffusion of temperature, and is called the thermometric conductivity or, more shortly, the diffusivity.

proportional to the rate of variation - dc/dx of the concentration c with the distance x, so that the number of gramme-molecules of solute which, in a time dt, cross an area A of a long cylinder of constant cross section is dN = - DA(dc/dx)dt, where D is a constant known as the diffusion constant or the diffusivity.