Refined Schwarz-Christoffel (SC) conformal transformations allow us to perform reliable quantitative evaluation of the accuracy of local computation of electric and magnetic fields with limited effort, which can be useful to complement well known comparisons of global results. In this paper some examples are presented for mesh point potentials obtained by means of finite difference (FD) methods, but it is possible that similar considerations will be useful in the case of finite element methods (FEM) or meshless computations too.
An automated procedure based on evolutionary computation and Finite Element Analysis (FEA) is proposed to synthesize the optimal distribution of nanoparticles (NPs) in multi-site injection for a Magnetic Fluid Hyperthermia (MFH) therapy. Evolution Strategy and Non dominated Sorting Genetic Algorithm (NSGA) are used as optimization procedures coupled with a Finite Element computation tool.
The classic relationships concerning the harmonic content in the air gap field of three-phase machines are presented in form of series of rotating waves. The same approach is applied to modeling of permanent magnet motors with fractional phase windings. All main reasons of non-sinusoidal shape of flux density distribution, namely, magnets’ shape and their placement, slotting, magnetic saturation and eccentricity are also related to their counterparts in modal-frequency spectrum. The Fourier 2D spectrum of time-stepping finite element solution is confronted with results of measurements, with special attention paid to accuracy of both methods.
In the paper, methodologies for the magnetic field simulation in an axial flux permanent magnet coreless (AFPMC) motor have been proposed and discussed. Two approaches have been considered and investigated, both based on representing the 3D field distribution by superimposing axisymmetric 2D patterns. The first of studied approaches applies directly to the Biot-Savart law while the second uses a 2D axisymmetric finite element method. The selected results of magnetic field distributions and electromagnetic torque characteristics for the considered AFPMC motor have been presented and compared with results obtained using the commercial FEM package 'Maxwell'. The elaborated algorithms have been incorporated into the design routines allowing multi-parameter optimisation of the considered motor construction.
Mixed boundary-value problem for periodic baffles in acoustic medium is solved with help of the method developed earlier in electrostatics. The nice feature of the method is that the resulting matrices are relatively easy for computations and that the results satisfy exactly the energy conservation law. Illustrative numerical examples present the wave-beam steering (in the far-field) in a baffle system that may be considered as a model of one-dimensional ultrasonic transducer array.
The main thesis of this paper is the assertion that, in contrast to the prevailing opinion about the decline or deep crisis of the intelligentsia, it is precisely this social group—and especially its elite—that is the dominant actor in social life. This thesis emerges from an analysis of the role of the intelligentsia, using ‘longue durée’ categories and also the broader international perspective of ‘world system theory’, in which Poland is assigned to the (semi)-periphery. Elements of Pierre Bourdieu’s theory, particularly the idea of cultural capital and the field of power, are an important theoretical poin in the author’s argument. In this view, the structurally privileged position of the intelligentsia in Poland is understood as an aspect of the specific configuration of the Polish field of power, in which—at least since the end of the First World War—cultural capital turns out to be the strongest and most stable dimension in the creation and reproduction of elite social positions.
The article presents scientific achievements of Alfred Nobel Memorial Prize Laureates in economic sciences in 2019: Esther Duflo, Abhijit Banerjee, and Michael Kremer. The paper describes their contribution to the research on the sources of poverty in the world and the ways of alleviating it, and their contribution to the development of experimental research in social sciences using randomized control trials (RCT). In this context, the authors explain the reasons for growing popularity of this approach in development economics and discuss its strengths and weaknesses.
A novel method of active noise control using adaptive radiation sound sources is investigated. A finite element model of a modal enclosed sound field is excited harmonically, representing a noise field in the low-frequency range. The control sources are comprised of elementary dipole sources for which the driving signals are adjusted by an optimization method. Two set-up cases of the proposed compound sources are investigated. The coupling of the control sources with the modal sound field is discussed. The simulated performance of the proposed method is compared with that of a system with distributed simple sources and the results show the effectiveness of the sources with adaptive radiation for active noise control in small enclosures.
A ship built from ferromagnetic steel disturbs the uniformity of the Earth’s magnetic field. Changes of ship’s signature are due to the magneto-mechanical interaction of the hull with the Earth’s magnetic field. The ship’s magnetic field can be detected by a magnetic naval mine. For this reason, the vessel has to be demagnetized. There are several methods of ship’s de-perming. The results of experimental and computer simulations of the ship’s de-perming process using coils lying on the seabed are presented in this paper. The simulation of the de-perming process with a hysteresis model of ship’s steel was carried out in Opera-3d 18R2. The laboratory experiments were carried out using a physical ship’s model, several Helmholtz coils, magneto-resistive sensors, etc. The experiments and computer simulations have shown that ship’s de-perming with coils lying on the seabed is possible. The values of coil currents are over dozen times greater than those used in the standard method.