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Murta-Pina, J., P. Pereira, J. M. Ceballos, A. Alvarez, N. Amaro, A. Pronto, J. Silva, and P. Arsenio, "Validation and Application of Sand Pile Modeling of Multiseeded HTS Bulk Superconductors", Applied Superconductivity, IEEE Transactions on, vol. 25, no. 3, pp. 1-5, June, 2015. AbstractWebsite

Sand pile and Bean models have already been applied to describe single grain HTS bulks. An extension to that approach was used to model multiseed bulks, needed for several practical applications as electric motors or flywheels with superconducting bearings. The use of genetic algorithms was then proposed to determine intra- and intergrain current densities, and application to two and three seeds samples using trapped flux experimental measurements was exemplified. However, this model assumed some simplifications, as equal properties in grain boundaries between neighboring grains. In this paper an extension to this methodology is proposed and evaluated by analyzing measurements performed in plans at different distances from surfaces of samples with three seeds. Discussion of its influence on a practical application is also explored.

Coito, F., H. Fino, and P. Pereira, "Variability-Aware Optimization of RF Integrated Inductors in Nanometer-Scale Technologies", Integrated Circuits for Analog Signal Processing, New York, Springer-Verlag, pp. 271-287, 2013. Abstract

Progressive scaling of CMOS technology towards nanoscale regime enables the design of highly integrated systems for the wireless communications market. As technology continues to scale, the variability in process parameters may cause significant deviations in device behaviour. The complexity of designing spiral inductors has lead to the development of multi-objective optimization based design methodologies yielding the generation of Pareto-optimal surfaces. However, the variability of the process parameters is usually ignored, yielding the selection of ideally optimal solutions in detriment of quasi-optimal solutions that may prove to be better, should the robustness against process parameter variation be accounted for. We propose the generation of an extended Pareto front containing both optima and quasi-optima solutions. Finally information on the robustness to process parameter variations, is used for electing the best design solutions.The evaluation of the extended set of sub-optima solutions requires methods capable to find the set of local optima, since solutions that are close to each other in the performance index space may be very distant in the design parameter space.

Pereira, P., and H. Fino, "VCOSYM -an application for the automatic design of ring VCOS", Proc. 12th IEEE Int. Conf. Electronics, Circuits and Systems ICECS 2005, pp. 1–4, 2005. Abstract

This paper presents an application for the automatic design of ring VCOs. In this application a VCO model based on the Npower transistor model is considered as a away of granting the accuracy of results for submicron technologies. In order to easily integrate any VCO previously designed into a PLL automatic design tool, a corresponding linear model of the VCO is automatically generated, yielding a simple and precise characterization for higher level system design. The design of a 150 MHz VCO using a seven stage ring topology is presented. The validity of the design obtained is checked against Hspice simulation of the circuit.