P. Carbone

A. De Angelis, J. Schoukens, K. R. Godfrey et al.

The problem of measuring the best linear approximation of a nonlinear system by means of multilevel excitation sequences is analyzed. A comparison between different types of sequences applied at the input of Wiener systems is provided by numerical simulations and by experiments on a practical circuit including an analog filter and a clipping nonlinearity. The performance of the sequences is compared with a white Gaussian noise signal for reference purposes. The theoretical characterization of the best linear approximation when using randomized constrained sequences is derived analytically for the cubic nonlinearity case. Numerical and experimental results show that the randomized constrained approach for designing ternary sequences has a low sensitivity to both even and odd order nonlinearities, resulting in a response close to the actual response of the underlying linear system.

M. T. Horsch, C. Niethammer, G. Boccardo et al.

By introducing a common representational system for metadata that describe the employed simulation workflows, diverse sources of data and platforms in computational molecular engineering, such as workflow management systems, can become interoperable at the semantic level. To achieve semantic interoperability, the present work introduces two ontologies that provide a formal specification of the entities occurring in a simulation workflow and the relations between them: The software ontology VISO is developed to represent software packages and their features, and OSMO, an ontology for simulation, modelling, and optimization, is introduced on the basis of MODA, a previously developed semi-intuitive graph notation for workflows in materials modelling. As a proof of concept, OSMO is employed to describe a use case of the TaLPas workflow management system, a scheduler and workflow optimizer for particle-based simulations.