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2.4 the continuous deterministic process

In many cases it is not possible to divide the process into a finite number of discrete stages, since the state of the stream is transformed in a continuous manner through the process.

We replace r, the number of the stage from the end of the process, by t, a continuous variable which measures the `` distance '' of the point considered from the end of the process.

The word distance is used here in a rather general sense ; ;

it may in fact be the time that will elapse before the end of the process.

If T is the total `` length '' of the process, its feed state may be denoted by a vector p(T) and the product state by p(Q).

P denotes the state at any point T and Q the vector of operating variables there.