RHSICSTR:

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   Model of CSTR with an irreversible first order reaction
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   Form:
   xDot = RHSICSTR( x, t, d )
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   ------
   Inputs
   ------
   x           (4,1) State [composition;temperature]
   t           (1,1) Time
   d           (1,1) data structure
                     .dA    (1,1) 
                     .gamma (1,1)
           b          .b     (1,1)
                     .beta  (1,1)
                     .u     (1,1) Control
   -------
   Outputs
   -------
   xDot        (2,1) State derivative

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   Reference: Henson, M. A. and D. E. Seborg. (1997.) Nonlinear Process
              Control Prentice-Hall. pp. 398-399.
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