Diego Martinez Prata

Comparative analysis of robust estimators on nonlinear dynamic data reconciliation

Abstract This paper presents a comparative performance analysis of various robust estimators used for nonlinear dynamic data reconciliation process subject to gross errors. Robust estimators based on cost functions derived from robust probability theory reduce the effect of gross errors on the reconciled data, avoiding the traditional iterative requirement procedures. The following robust probability functions were compared in this paper: Cauchy, Fair, Hampel, Logistic, Lorentzian, Normal Contaminated and Welsch. As a benchmark for this study it was adopted a nonlinear CSTR frequently reported in the process data reconciliation literature. The comparative analysis was based on the ability of the reconciliation approaches for reducing gross errors effect. Although the presence of constant biases has represented a problem for all the analyzed estimators, Welsch and Lorentzian cost functions, in this order, have shown better global performance.

Optimal wavelet signal compression as an efficient alternative to investigate molecular dynamics simulations: application to thermal and solvent effects of MRI probes

Currently, cancer is one of the most serious problems facing humanity, and one of the most widely used and versatile diagnostic techniques is magnetic resonance imaging (MRI), which may require an injection of contrast agents (CAs). CAs are paramagnetic compounds capable of increasing the relaxation rate of water protons, thereby obtaining clearer MRI examination images. In this work, the solvent and thermal effects on spectroscopic parameters of [Fe(H2O)6]2+, [Mn(H2O)6]2+, [Gd(H2O)8]3+, and γ-Fe2O3, coordinated to explicit water molecules, were studied in light of the classical and quantum methods. For the classical part of the simulation, a new method of selection of configurations from the molecular dynamics simulations, denominated optimal wavelet signal compression algorithm (OWSCA), is presented. Our findings indicate that OWSCA leads to a good agreement with the experimental available data and the thermal effects greatly influence our system. Thus, the molecular dynamics calculations are important for this type of system. Our results show the γ-Fe2O3 as a promising alternative to conventional contrast agents.

Nonlinear Dynamic Data Reconciliation in Real Time in Actual Processes

Abstract In this work, some recent developments regarding the real time monitoring of industrial processes based on robust data reconciliation and gross error detection are reviewed. Particularly, robust data reconciliation and gross error detection are performed on line and in real time in a real polymerization process.

Application of Scilab/Xcos for process control applied to chemical engineering educational projects

The study of process control applied to chemical engineering problems can be significantly improved by the use of simulation packages. However, it has been noted that few works have been focusing on elucidation of the use of open source packages for academic projects on process control. In fact, there is few online discussion groups aimed to the application of Xcos® package for chemical engineering projects. Given this, this work aims to apply the Xcos® for studying the implementation of the process control theory applied to chemical engineering projects, focusing on the development of control loops block diagrams, PID control tuning, and process response analysis. The purpose of the application is developing a virtual environment for academic discussion and repository of examples. The results of two benchmark case studies are illustrated, showing that the problems can be easily modified, allowing the student to solve other similar examples for future applications. For the first case, the settling time ranged from 24.067 to 72.492 min, while for the second case the stabilization time ranged from 5.301 to 20.904 min.The results evidence that the Xcos® software can be widely applied by the academic community, due to its simplicity and robustness in demonstrating the principal aspects of control theory.