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ISOFIT - A PROGRAM FOR FITTING SORPTION ISOTHERMS TO EXPERIMENTAL DATA
Citation:
MATOTT, L. S. AND A. J. RABIDEAU. ISOFIT - A PROGRAM FOR FITTING SORPTION ISOTHERMS TO EXPERIMENTAL DATA. ENVIRONMENTAL MODELLING & SOFTWARE. Elsevier Science, New York, NY, 23(5):670-676, (2008).
Impact/Purpose:
The primary goals are to: (1) Construct a 400-node PC-based supercomputing cluster supporting Windows and Linux computer operating systems (i.e. SuperMUSE: Supercomputer for Model Uncertainty and Sensitivity Evaluation); (2) Develop platform-independent system software for the management of SuperMUSE and parallelization of EPA models and modeling systems for implementation on SuperMUSE (and other PC-based clusters); (3) Conduct uncertainty and sensitivity analyses of the 3MRA modeling system; (4) Develop advanced algorithmic software for advanced statistical sampling methods, and screening, localized, and global sensitivity analyses; and (5) Provide customer-oriented model applications for probabilistic risk assessment supporting quality assurance in multimedia decision-making.
Description:
Isotherm expressions are important for describing the partitioning of contaminants in environmental systems. ISOFIT (ISOtherm FItting Tool) is a software program that fits isotherm parameters to experimental data via the minimization of a weighted sum of squared error (WSSE) objective function. ISOFIT supports a number of isotherms, including several dual-mode isotherms that combine Freundlich, Langmuir, and Polanyi expressions with a linear partitioning term. To minimize the WSSE objective function, ISOFIT utilizes a hybrid optimization procedure that combines particle swarm optimization with Levenberg-Marquardt nonlinear regression. An initial swarm optimization step identifies promising solutions while circumventing local minima and the follow-on regression step provides local refinement and facilitates the calculation of numerous regression statistics. To demonstrate ISOFIT and evaluate its performance, the program was applied to a readily available sorption dataset and benchmarked against results generated using the MS Excel solver package.