DECAY is a program for scheduling multiple feeds on parallel units. The performance of each unit, is assumed to decrease with time, requiring then a planed mantainance to restore its performance. A mixed-integer nonlinear programming (MINLP) model is used according to the paper of Vipul Jain and Ignacio E.Grossmann, "Cyclic Scheduling and Mantainance of Parallel Process Units with Decaying Performance", AICHE J., 44, 1623-1636 (1998). Optimization trade-off is between the performance of the units, and the mantainance costs and the loss of production due to shutdowns.

There are three main results given by the model: 
a)	Assignment of feeds to different units.
b)	Processing time of each feed on different units.
c)	Number of subcycles of each feed on different units.

The way this interface works is through the use of different menus; it is flexible and easy to use. Given the data of the problem, as it is indicated below, DECAY creates a new GAMS file containing the model equations and optimizes the problem using the outer approximation code DICOPT.

DECAY has been developed by Gabriela Garcia under the supervision of Ignacio E.Grossmann.