Level measurement Terms Links

The three historical approaches to certification mentioned above were recently expanded to identily seven modes that are used at NIST for value assignment for chemical composition (May et al. 2000). These seven modes and the resulting values are summarized in Table 3.13. The basic principles of value assignment remain unchanged however, these modes now provide a well-defined link between the process used for value assignment and the definition of the assigned value (i.e. certified, reference, or information value). The terms described above provide a clear indication of the level of confidence that NIST has in the accuracy of the assigned value. The definition of a certified value implies that NIST must be involved in the measurement process for the value to be classified as a NIST certified value (see modes 1-3 in Table 3.13). Thus, modes 4 and 7, which do not involve NIST measure-... 

The team also states the action level in numerical terms and verifies that the proposed measurement methods have adequate sensitivity to meet the stated action levels. Finally, the team develops a decision rule expressed as an if... then statement that links the parameter of interest, the scale of decision-making, the action level, and the alternative action. 

Hierarchies, such as primary, secondary, and working level, or certified RMs and RMs are extensively used in describing traceability chains. Whilst such terms can be useful in explaining processes and links, they can also be confusing. For this reason their use has been limited in this paper. It is considered preferable to describe hierarchies in terms of the associated uncertainties. It can also be noted that, whereas in physical measurement it is common to have a hierarchy of references of the same basic type (e.g., a series of mass standards), this is rare in chemical measurement where the chain usually contains only one chemical RM, linked to a higher reference by a measurement process. 

The main objective of performing kinetic theory analyzes is to explain physical phenomena that are measurable at the macroscopic level in a gas at- or near equilibrium in terms of the properties of the individual molecules and the intermolecular forces. For instance, one of the original aims of kinetic theory was to explain the experimental form of the ideal gas law from basic principles [65]. The kinetic theory of transport processes determines the transport coefficients (i.e., conductivity, diffusivity, and viscosity) and the mathematical form of the heat, mass and momentum fluxes. Nowadays the kinetic theory of gases originating in statistical mechanics is thus strongly linked with irreversible- or non-equilibrium thermodynamics which is a modern held in thermodynamics describing transport processes in systems that are not in global equilibrium. 

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