No. 4, 2005


Jaroslav Franek, Mojmir Kollar : Remembering a hundred years since publishing the theory of relativity, pp.307-318

In 2005, all civilised world is reminding the 100 years anniversary of publishing the original work on special theory of relativity by Albert Einstein. This contribution is a brief review of its principal ideas in the field of electrodynamics.

Jan Hlina, Frantisek Chvala : Application of polynomial approximation to analytical solution of Abel inversion of radiation profiles in a thermal plasma jet, pp.319-322

A method for solution of Abel integral equation describing the radial distribution of radiation intensity in plasma jets is presented. It is based upon a polynomial approximation of the measured side-on radiation profile. An application of Abel inversion then leads to an analytic expression for the relevant approximation of the radial distribution.

Miros Pirner, Shota Urushadze : Parametric study of liquid damper, pp.323-346

In earlier works (see [1]) the authors studied the movement of liquids of different viscosity (water, methanol, glycerine) in a rectangular tank which had two degrees of freedom: horizontal movement and rotation around its axis, the position of which was determined by the relation between the horizontal movement and the rotation of the tank as required.

All previous studies were made in the laboratory using the equipment enabling such horizontal tank excitation as to afford its forced movement the given amplitude within the whole frequency range. The rotary movement is not forced, depending on the afore mentioned axis position and the parameters of the experimental plant; the parameters were determined by tank rotation. In all preceding studies the excitation was harmonic.

In this new work the authors studied the behaviour of the liquid during horizontal excitation which could be characterized as random, described within the frequency range f1 = 0.5Hz to f2 = 2Hz by the power spectral density of the excitation force. The results of their last study were applied to the reduction of the dynamic response of a steel footbridge in Plzen.

Apart from that they analyze the influence of further characteristics of the damper and its liquid as indicated by the headings of individual paragraphs.

Vaclav Nenicka, Jiri Sonsky, Vladimir Dolinek : Quasi-stationary heat flow diagnostics in plasma jets, pp.347-384

The vortex structures in free plasma flow are identified using the information on the radiation intensity scanned in two mutually perpendicular directions by the CCD camera. Quasi-stationary regimes of free plasma flow are characterized by vortex structures in heat flows, noted for dynamical changes of the vorticity along the axis of the jet. The variant discussed in the paper makes it possible to identify the changes in dynamics by determining a three-dimensional course of the heat flow vector. The arrangement of the vortex structures generated by the vector potential is investigated considering a principal role of the product of enthalpy and flow velocity. The evolution of radiation intensity and dynamics of vortex structures in both the axial and radial direction about the jet's core is captured using the series of 8 shots within time interval of 100ms. The analysis of vortex dynamics at flow rates 25slm and 40slm and electrical currents 150A and 200A is presented.

To determine dynamics of vortex structures, we used algorithms of the MATLAB program, specifically the instructions 'streamline' and 'streamtube'. The presented results prove occurrence of several dynamic regimes of a vortex type in a quasi-stationary heat flow of free plasma flow. The occurrence and position of the vortex type regimes depends not only on flow rates of gas and on electric input but significantly also on the position of the diagnosed vortex structures towards the axis and orifice of the jet.

Zygmunt Pi�tek : Transient electromagnetic field in a conducting tubular workpiece, pp.385-398

In the paper we determine the transient electromagnetic field in a conducting tubular workpiece placed in external longitudinal sine-shaped magnetic field using the solution of Bessel equation in the cylindrical co-ordinates, and also applying the integral Laplace transform. The resulting equations are the basis for calculation and graphs of space-time distributions, attenuation and diffusion of the magnetic field strength and the current density in the tubular workpiece. The resulting equations can be used to describe volume density of the power lost in the tubular workpiece and to determine the equivalent parameters of the inductor-tubular work system.

Leslaw Topor-Kaminski, Marian Pasko : Realisations of general models of RMS-DC converters in ELIN-type circuits, pp.399-406

A general conception of the realisation of the RMS-DC converter using selective internal-nonlinear circuits (integrators) is described. Block diagrams of RMS-DC converters obtained from basic circuit for power function selected for exemplary exponents are presented and discussed. On their bases a few versions of the converter realisation using non-linear blocks with involution and ln-exp transition functions are created