Retraction process, effect temperature

In the worse case, where either sample temperature, pressure or reactor integrity issues make it impossible to do otherwise, it may be necessary to consider a direct in situ fiber-optic transmission or diffuse reflectance probe. However, this should be considered the position of last resort. Probe retraction devices are expensive, and an in situ probe is both vulnerable to fouling and allows for no effective sample temperature control. Having said that, the process chemical applications that normally require this configuration often have rather simple chemometric modeling development requirements, and the configuration has been used with success. 

To break the loop of cause-and-effect relationships, we make the unqualified assumption that Op2, the variable denoting the human operator, obtains its value from relationship (17) i.e., the operator responds to the temperature in the reactor (T ) and not vice versa. This assumption is then catalogued, as Assumption-1, so that it may be retracted at a later stage, as required. Such retraction allows the causality that emanates from the set of process equations to be modified. Once we have eliminated Eq. (17) and the column corresponding to variable Op, we can repeat the steps of the output set assignment (see Section IV.B), and find that F, obtains its value from Eq. (15). The set of input and output assignments, made so far, establish the causality between... 

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