Numerical modelling of the optical demultiplexer photonic structures

Photonic structures and their application are one of the most intensively studied areas of modern optics. They are used in devices such as blue lasers, optical fibres or optical add-drop multiplexers. The paper describes the possibility of designing the photonic structure of the optical demultiplexer using the application written by the authors

ANALYSIS OF EFFECTIVE PROPERTIES OF PIEZOCOMPOSITES BY THE SUBREGION BEM-MORI-TANAKA APPROACH

Recently, many approaches have been proposed to estimate the effective properties of composites. The most typical are: the self-consistent method and the Mori-Tanaka method. However, they are restricted to simple geometries of phases. Also for complex constitutive laws the analytical results are complicated. On the other hand, the combination of numerical methods and these approaches gives an efficient computational scheme for estimating effective properties of composite materials. In this paper the hybrid subregion boundary element method (BEM) and Mori-Tanaka approach is implemented to solve coupled field equations of linear piezocomposites in the unit cell approach and then to determine the effective properties . To obtain the BEM fundamental solutions, the Stroh formalism is used. The numerical examples demonstrate an effectiveness of the BEM-Mori-Tanaka approach

Kansa Method for Unsteady Heat Flow in Nonhomogenous Material with a New Proposal of Finding the Good Value of RBF’s Shape Parameter

New engineering materials exhibit a complex internal structure that determines their properties. For thermal metamaterials, it is essential to shape their thermophysical parameters’ spatial variability to ensure unique properties of heat flux control. Modeling heterogeneous materials such as thermal metamaterials is a current research problem, and meshless methods are currently quite popular for simulation. The main problem when using new modeling methods is the selection of their optimal parameters. The Kansa method is currently a well-established method of solving problems described by partial differential equations. However, one unsolved problem associated with this method that hinders its popularization is choosing the optimal shape parameter value of the radial basis functions. The algorithm proposed by Fasshauer and Zhang is, as of today, one of the most popular and the best-established algorithms for finding a good shape parameter value for the Kansa method. However, it turns out that it is not suitable for all classes of computational problems, e.g., for modeling the 1D heat conduction in non-homogeneous materials, as in the present paper. The work proposes two new algorithms for finding a good shape parameter value, one based on the analysis of the condition number of the matrix obtained by performing specific operations on interpolation matrix and the other being a modification of the Fasshauer algorithm. According to the error measures used in work, the proposed algorithms for the considered class of problem provide shape parameter values that lead to better results than the classic Fasshauer algorithm

Recurrent thrombosis of a mitral mechanical heart valve prosthesis during puerperium - a case report

Abstract: A case of a 27-year-old female with prosthetic mitral valve is presented. Prolonged anticoagulation therapy was continued during pregnancy without complications. During puerperium, the dose of subcutaneous low molecular weight heparin was reduced due to subcutaneous blood effusions. Subsequently, the patient developed acute left ventricular heart failure due to prosthetic valve thrombosis. She underwent urgent surgery with new prosthetic valve implantation. Two weeks later she suffered another episode of acute mitral prosthetic valve thrombosis which was effectively treated with intravenous heparin. Difficulties concerning prolonged anticoagulation during pregnancy and puerperium in patients with prosthetic valves are discussed