Modeling challenges in computational electromagnetics:large planar multilayered structures and finite-thickness irises

Abstract Printed multilayered media with metallizations embedded between dielectric layers are one of the most successful technologies for manufacturing planar structures with a good performanceto-price ratio. These structures range from PC board circuits, through cavity backed antennas and antenna arrays used in satellite communications, to waveguide filters. The approach most commonly used to model and analyze the aforementioned structures is the Integral Equation (IE) technique solved with Method of Moments (MoM). Applying IE-MoM with subsectional basis functions to electromagnetically large structures is demanding in terms of both computer memory allocation and time needed to solve the problem. Computationally efficient techniques are thus needed to accelerate the IE-MoM procedures and allow modeling of large circuits and antennas on standard desktop PCs. Subdomain Multilevel Approach (SMA) with Macro-Basis Functions (MBF) is one of the acceleration techniques, developed in our laboratory. Its application to modeling large antenna arrays has already proven to be very efficient. However, this technique can be improved, especially when MoM matrix filling time is concerned. This thesis proposes an improvement of the SMA using equivalent moments in computing the interactions between macro-basis functions. It shows that, without significant loss of accuracy, we obtain a two-fold gain in computational time for structures with the number of unknowns of the order 104. In structures operating at higher frequencies (thin films in millimeter and submillimeter wave bands) or with self supporting metallic plates, the thickness of metallic screens must be taken into account. Multilayered structures with apertures (holes) in thick conducting screens can be accurately modeled using the equivalence theorem and magnetic currents introduced at both aperture interfaces. This approach, however, doubles the number of unknowns as compared to that one of the zero-thickness case. Moreover, the thick aperture problem asks for the computation of cavity Green's functions, which is a difficult and time-consuming task for apertures of arbitrary cross-sections. This thesis addresses the problem of scattering by apertures in thick conducting screens by introducing an approximate and computationally efficient formulation. This formulation consists in treating the thick aperture as an infinitely thin one and in using the correction term in integral equation kernel that accounts for the screen thickness. The number of unknowns remains the same as in the zero-thickness screens and evaluation of complicated cavity Green's functions is obviated, which yields computationally efficient routines. The technique is successfully applied to self-supporting aperture antennas and thick irises within multilayered rectangular waveguides giving good results for apertures whose thickness is smaller than their lateral dimensions

Integral Equation Modeling of Waveguide-Fed Planar Antennas

This paper presents a method for the analysis of planar multilayered waveguide-fed antennas. The method combines mixed-potential integral equations (for laterally open regions) and modal field integral equations (for laterally closed regions) with a seamless transition between the two domains. The method has been implemented in a numerical tool and the simulation results of two waveguide-fed microstrip structures have been presented. The results are in good agreement with both measurements and simulations obtained with other commercial electromagnetic tools. Comparisons in terms of memory occupation and simulation time have also been performed

Mitochondrial physiology

As the knowledge base and importance of mitochondrial physiology to evolution, health and disease expands, the necessity for harmonizing the terminology concerning mitochondrial respiratory states and rates has become increasingly apparent. The chemiosmotic theory establishes the mechanism of energy transformation and coupling in oxidative phosphorylation. The unifying concept of the protonmotive force provides the framework for developing a consistent theoretical foundation of mitochondrial physiology and bioenergetics. We follow the latest SI guidelines and those of the International Union of Pure and Applied Chemistry (IUPAC) on terminology in physical chemistry, extended by considerations of open systems and thermodynamics of irreversible processes. The concept-driven constructive terminology incorporates the meaning of each quantity and aligns concepts and symbols with the nomenclature of classical bioenergetics. We endeavour to provide a balanced view of mitochondrial respiratory control and a critical discussion on reporting data of mitochondrial respiration in terms of metabolic flows and fluxes. Uniform standards for evaluation of respiratory states and rates will ultimately contribute to reproducibility between laboratories and thus support the development of data repositories of mitochondrial respiratory function in species, tissues, and cells. Clarity of concept and consistency of nomenclature facilitate effective transdisciplinary communication, education, and ultimately further discovery

Behavioral high-frequency modeling of electrical motors

Reliable simulations of electromagnetic interference in motor drive power electronic systems ask for accurate high-frequency motor models. A methodology for creating frequency dependent behavioral circuit models of ac electrical motors is presented in this paper. It is based on the rational function fitting of measured motor network parameters. Stable, causal, and passive equivalent circuits are obtained and their accuracy verified by comparing the simulation results with frequency domain common- and differential-mode measurements

Can Tournament Selection Improve Performances of the Classical Particle Swarm Optimization Algorithm?

Abstract — Particle Swarm Optimization (PSO) algorithm is known to be very efficient solution for electromagnetic (EM) optimization problems. In this paper we show that binary tournament selection applied to PSO algorithm further speedsup its convergence. Having in mind that EM simulation is the most time-consuming part of the optimization, reducing the overal number of iterations (EM solver calls) is of a paramount relevance. I