Jacek Ptaszny

Hybrid artificial immune system in identification of room acoustic properties

The paper deals with an application of a hybrid artificial immune system (HAIS) to the identification problems. The HAIS is applied to identify complex impedances of room walls. This approach is based on the mechanism discovered in biological immune systems. The numerical example demonstrates that the method based on immune computation is an effective technique for solving computer aided in identification problem.

Hybrid particle swarm optimizer and its application in identification of room acoustic properties

The paper deals with an application of an hybrid particle swarm optimizer (HPSO) to identification problems. The HPSO is applied to identify complex impedances of room walls and it is based on the mechanism discovered in the nature during observations of the animals social behaviour and supplemented with some additional gradient information. The numerical example demonstrate that the method based on hybrid swarm optimization is an effective technique for computing in identification problems.

Numerical homogenization by using the fast multipole boundary element method

The paper concerns the numerical homogenization of non-homogeneous linear-elastic materials by using the fast multipole boundary element method (FMBEM). Application of the FMBEM allows for the analysis of structures with larger number of degrees of freedom (DOF) in comparison to the conventional collocation BEM, which has at least the quadratic complexity. The FMBEM is convenient in the numerical homogenization by modelling of complex representative volume elements. In this article two examples of homogenization are presented. The first one concerns a porous material, and the second one – a composite material. The obtained results are in good agreement with analytical, semi-empirical and empirical models, and also with numerical results presented by other authors.

Evaluation of the FMBEM efficiency in the analysis of porous structures

Purpose The purpose of this paper is to evaluate the efficiency of the Fast Multipole Boundary Element Method (FMBEM) in the analysis of stress and effective properties of 3D linear elastic structures with cavities. In particular, a comparison between the FMBEM and the Finite Element Method (FEM) is performed in terms of accuracy, model size and computation time. Design/methodology/approach The developed FMBEM utilizes 8-node Serendipity boundary elements with numerical integration based on the adaptive subdivision of elements. Multipole and local expansions and translations involve solid harmonics. The purposed model is used to analyse a solid body with two interacting spherical cavities and to predict the homogenized response of a porous material under linear displacement boundary condition. The FEM results are generated in commercial codes Ansys and MSC.Patran/Nastran and the results are compared in terms of accuracy, model size and execution time. Analytical solutions available in the literature are a...

Optimization of Porous Structure Effective Elastic Properties by the Fast Multipole Boundary Element Method and an Artificial Immune System

An application of the fast multipole boundary element method (FMBEM) and an artificial immune system (AIS) to the optimization of porous structure effective elastic properties is presented. The FMBEM allows one to model complex geometries with much lower number of degrees of freedom in comparison to the finite element method, that is usually applied in computational homogenization. Representative volume elements (RVEs) are modelled, with displacement boundary conditions corresponding to a given strain state in the macro scale. Effective elastic constants of the material are calculated by using the averaged strains and stresses. Design variables considered in the optimization problem describe the geometry. The minimized objective function involves a metric that allows one to calculate the distance between two elasticity tensors: a current solution and a reference tensor that defines the desired properties. A benchmark problem of porous structure with maximized effective bulk modulus is solved.