There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality.

Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

I and i

A criterion is given for the convergence of numerical solutions of the Navier-Stokes equations in two dimensions under steady conditions. The criterion applies to all cases, of steady viscous flow in two dimensions and shows that if the local ' mesh Reynolds number ', based on the size of the mesh used in the solution, exceeds a certain fixed value, the numerical solution will not converge.

On the Navier-Stokes equations

The electromagnetic fields within a detailed model of the human eye and its surrounding bony orbit are calculated for two different frequencies of plane-wave irradiation: 750 MHz and 1.5 GHz. The computation is performed with a finite-difference algorithm for the time-dependent Maxwell's equations, carried out to the sinusoidal steady state. The heating potential, derived from the square of the electric field, is used to calculate the temperatures induced within the eyeball of the model. This computation is performed with the implicit alternating-direction (IAD) algorithm for the heat conduction equation. Using an order-of-magnitude estimate of the heat-sinking capacity of the retinal blood supply, it is determined that a hot spot exceeding 40.4/spl deg/C occurs at the center of the model eyeball at an incident power level of 100 mW/cm/sup 2/ at 1.5 GHz.

Computation of the Electromagnetic Fields and Induced Temperatures Within a Model of the Microwave-Irradiated Human Eye

Transcranial magnetic stimulation in basic and clinical neuroscience: A comprehensive review of fundamental principles and novel insights.

We discuss the transmission line (TL) theory and its application to the problem of lightning electromagnetic field coupling to TLs. We start with the derivation of the general field-to-TL coupling equations for the case of a single-wire line above a perfectly conducting ground. The derived equations are solely based on the thin-wire approximation and they do take into account high-frequency radiation effects. Under the TL approximation, the general equations reduce to the Agrawal et al. field-to-TL coupling equations. After a short discussion on the underlying assumptions of the TL theory, three seemingly different but completely equivalent approaches that have been proposed to describe the coupling of electromagnetic fields to TLs are presented. The derived equations are then extended to deal with the presence of losses and multiple conductors and expressions for the line parameters, including the ground impedance and admittance, are presented. The time-domain representation of the field-to-TL coupling equations, which allows for a straightforward treatment of nonlinear phenomena as well as the variation in the line topology, is also described. Solution methods in the frequency domain and in the time domain are given and application examples with reference to lightning-induced voltages are presented and discussed. Specifically, the effects of ground losses and corona are illustrated and discussed. When the traveling voltage and current waves are originated from lumped excitation sources located at a specific location along a TL (direct lightning strike), both the corona phenomenon and ground losses result, in general, in an attenuation and dispersion of propagating surges along TLs. However, when distributed sources representing the action of the electromagnetic field from a nearby lightning illuminating the line are present, ground losses and corona phenomenon could result in important enhancement of the induced voltage magnitude.

A Review of Field-to-Transmission Line Coupling Models With Special Emphasis to Lightning-Induced Voltages on Overhead Lines

The paper reviews some aspects of finite element modeling of magnetohydrodynamics (MHD) phenomena for fusion related research. Thus, Grand-Shafranov Equation (GSE) for plasma equilibrium has been solved for some simple excitation forms and the obtained numerical results for the rectangular and D-shape plasma, respectively have been presented. A good agreement with already published results in relevant literature has been shown. This paper should be referred as an opener to the numerical modeling of MHD phenomena for fusion related research.

A note on FEM modeling of some magnetohydrodynamics phenomena for application in fusion related research

The paper deals with the panel antenna modeling using NEC Win PRO v. 1.1 package. Base of antenna modeling would be wire construction. To achieve better performance and characteristics, several solutions for reflector and dipole will be proposed. Antenna with best results and attributes will be compared with technical data of APX907016 RFS antenna given by producer. The challenge in the design of a suitable antenna is overcoming the inherent relationships between gain, pattern beam width, the presence of pattern side and back lobes, and also the size of the antenna.

Modeling panel antenna in NEC

The paper deals with measures for evaluating the human exposure to signals with continuous spectra, such as signals radiated from power line communication systems (PLC), ground penetrating radar (GPR), or other ultra-wideband signals. A new approach is proposed, arising from the signal theory, where integrals of radiated field spectra are calculated from the measured field amplitudes. A computational example is presented, which deals with PLC signals; future work will deal with GPR signals.

A Note on Measures of Human Exposure to Signals with Continuous Spectra

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Advanced Modeling in Stochastic Computational Electromagnetics

This paper presents a novel approach for the calculation of the transient impedance of the horizontal electrode used as a synchronous generator grounding. When a short circuit occurs in the network, corresponding short-circuit current acts as an excitation source of the horizontal grounding electrode. Both short-circuit current and horizontal electrode impulse response, are defined in the time domain in a closed form representation. Transient impedance calculation is based on the novel derivation of the closed form time domain solution for short-current excitation. Some illustrative numerical results are provided, taking into account various parameters of the grounding system.

Dragan Poljak

Papers

A note on FEM modeling of some magnetohydrodynamics phenomena for application in fusion related research

Modeling panel antenna in NEC

A Note on Measures of Human Exposure to Signals with Continuous Spectra

Advanced Modeling in Stochastic Computational Electromagnetics

Transient Impedance of the Synchronous Generator Grounding Electrode due to Short Circuit Current