arXiv subjects

Wojciech Nawalaniec

Publications and source records attributed to Wojciech Nawalaniec.

3 recordsLinked to original sources

arXiv2019

Classifying and analysis of random composites using structural sums feature vector

The main goal of this paper is to present the application of structural sums, mathematical objects originating from the computational materials science, in construction of a feature space vector of 2D random composites simulated by distributions of non-overlapping disks on the plane. Construction of the feature vector enables the immediate application of machine learning tools and data analysis techniques to random structures. In order to present the accuracy and the potential of structural sums as geometry descriptors, we apply them to classification problems comprising composites with circular inclusions as well as composites with shapes formed by disks. As an application, we perform the analysis of different models of composites in order to formulate the irregularity measure of random structures. We also visualize the relationship between the effective conductivity of 2D composites and the geometry of inclusions.

cs.CE↗

arXiv2019

Effective conductivity of a random suspension of highly conducting spherical particles

Randomly distributed non-overlapping perfectly conducting spheres are embedded in a conducting matrix with the concentration of inclusions $f$. Jeffrey (1973) suggested an analytical formula valid up to $O(f^3)$ for macroscopically isotropic random composites. A conditionally convergent sum arose in the spatial averaging. In the present paper, we apply a method of functional equations to random composites and correct Jeffrey's formula. The main revision concerns the proper investigation of the conditionally convergent sum and correction the $f^2$-term. A new model of symbolic computations is developed in order to compute the effective conductivity tensor. The corresponding algorithm is realized up to $O(f^{\frac{10}3})$. The obtained formulae explicitly demonstrate the dependence of the effective conductivity tensor on the deterministic and probabilistic distributions of inclusions in the $f^2$-term, and in the $f^3$-term. This leads to the conclusion that some previous formulae presented as universal, i.e., valid for all random composites, may be actually applied only to dilute or to special composites when interaction between inclusions do not matter.

math-ph↗

arXiv2015

Effective Conductivity and Critical Properties of a Hexagonal Array of Superconducting Cylinders

Effective conductivity of a 2D composite corresponding to the regular hexagonal arrangement of superconducting disks is expressed in the form of a long series in the volume fraction of ideally conducting disks. According to our calculations based on various re-summation techniques, both the threshold and critical index are obtained in good agreement with expected values. The critical amplitude is in the interval $(5.14,5.24)$ that is close to the theoretical estimation $5.18$. The next order (constant) term in the high concentration regime is calculated for the first time, and the best estimate is equal to $(-6.229)$. Final formula is derived for the effective conductivity for arbitrary volume fraction.

cond-mat.stat-mech↗