Читать книгу Global Approaches to Environmental Management on Military Training Ranges - Tracey Temple - Страница 35

There are two types of material properties that must be determined. This first is the nature of the elements: are they finite or infinite element materials. In the case of characterizing military ranges, all materials can be assumed to be infinite element materials and therefore the theory of sampling (TOS) must be applied.

The second material property is the nature of the heterogeneity. There are two types of heterogeneity: compositional and distributional [18].

Compositional heterogeneity exists when the individual elements (particles) that make up the DU do not have exactly the same concentration of the analyte of interest. Compositional heterogeneity (CH) always exists to some degree.

Distributional heterogeneity (DH) exists when the individual elements that make up the decision unit are not randomly distributed throughout the entire DU. Examples of distributional heterogeneity are the settling of small, dense fines to the bottom of a container of soil and the uneven distribution of propellant residue across a weapons firing point. Like compositional heterogeneity, DH almost always exists and can be influenced by physical conditions. The magnitude and nature of CH and DH will vary for different materials.