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 maintenance to restore its performance. A mixed-integer nonlinear programming (MINLP) model is used according to Vipul Jain and Ignacio E.Grossmann (1998).

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.

This interface is written in language C and runs on Windows 98 or Windows-NT. The way this interface works is through different menus; it is flexible and easy to use. Given the data of the problem, DECAY creates a new GAMS file containing the model equations and optimizes the problem using subroutines of DICOPT++ and MINOS for the B&B algorithm.
DICOPT++ ( DIscrete and Continuos OPTimizer ) was developed by J. Viswanathan and Ignacio E. Grossmann at the Engineering Research Center (EDRC) of the Carnegie Mellon University . It is based on the extensions of the outer-approximation algorithm for equality relaxation strategy.

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

References for DECAY:

Vipul Jain. and I. E. Grossmann, Cyclic Scheduling of Continuous Parallel Process Units with Decaying Performance, AICHE Journal,1998, Vol. 44, No. 7, pp. 1623-1636.

Garcia-Ayala, Gabriela, Guidelines for Decay Interface, Carnegie Mellon University,
Engineering Design Research Center, Pittsburgh, PA 2000.