Lizandro S. Santos

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.

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.

Comparative Study of Optimization in Pultrusion with Pre-Heating and Die-Cooler Temperature for Improved Cure

Pultrusion is a composite manufacturing technique for processing continuous composite profiles with a constant cross section. In such system, energy and mass balances are used to model the thermal and kinetic behavior of the material during processing. This work aims to compare the results obtained in the recent literature, regarding thermal optimization of pultrusion. In the present analysis, an alternative thermal configuration has been suggested, with the objective of maximizing the mean degree of cure. A general-purpose FE software, ANSYS-CFX®, has been used to perform a three-dimensional (3D) conductive heat transfer analysis. Several case studies were conducted where the degree of cure was analyzed for varying heating scenarios. Results have shown that it is possible to get a higher cure in less process time if the die is isolated from the environment.