No. 3, 2000


Frantisek Chvala : On velocity distribution described by the nonlinear Boltzmann equation with boundary conditions and initial data, pp.221-227

The velocity distribution function of particles of a gas confined to a vessel is considered as the solution of the initial-boundary value problem for the nonlinear Boltzmann equation. An external force and a source of particles are included. By successive linearizations of the problem a sequence of iterated functions is constructed such that it converges, under specified hypotheses, to the velocity distribution function.

Marian Pasko, Janusz Walczak, Magdalena Uminska-Bortliczek : Optimization conditions for the electrical energy quality criterion and compensator synthesis in systems with nonsinusoidal waveforms, pp.229-240

Two problems have been presented in the paper: optimization of complex structures of electrical systems with nonsinusoidal waveforms, and synthesis of compensators for elimination of distortion and minimization of active power losses.

Bohumil Stadnik, Milena Jiraskova : Dependence of the human skin protection against the UV solar carcinoma radiation on the sunscreens and cosmetics layer thickness, pp.241-249

We show the human skin protection against the harmful UV solar carcinoma radiation is strongly dependent on the layer thickness of dermatological sunscreens and cosmetics. The protection properties of selected sunscreens and cosmetics with a higher number of sunscreen modifications are given.

Viktor Pekarek : Emission of electromagnetic waves through the medium of matter waves, genesis of photons in vacuum, pp.251-260

Despite the great effort to reconcile the quantum aspects with the wave representation, the existing theory is incapable of explaining the factual mechanism of energy transfers between matter and light by emission of electromagnetic waves. In particular, the hitherto known theory cannot restore the causal continuity between electrical frequencies (orbital oscillations of electrons) and radiated frequencies in atomic oscillators. Following de Broglie's idea of the particle-wave duality, matter waves of electrons appear to be the missing link in the interaction. Mathematical treatment indicates that it is the surges of the waves interference that are directly turned into the photons of radiation. This process takes place inside the interatomic vacuum that becomes a spring of quantized energy. The theory yields a new form of the hn law, defining a complete polychromatic structure of the hydrogen spectrum.

Jiri Klima : Mixed p-z approach for analytical analysis of power converters with periodic PWM, pp.261-279

A mixed p-z approach for the time analysis of converter systems containing periodically operated switches is described. The approach is applicable for all types of converters with an explicitly determined output voltage (converters with forced commutation). The mathematical model uses the Laplace and modified Z transforms. The solution is not dependent on the number of the pulses of the PWM pattern. Instead of solution of algebraic equations the change of switching instants is reflected in the solution only by a change in two values mk and nk. The derived equations are validated using a 3kW three-phase PWM inverter.

Ales Tondl : Dynamic absorbers for a pendulum system excited by vortex shedding, pp.281-293

Two types of dynamic absorbers are considered for the vibration quenching of a system which can be modelled as a free pendulum excited by vortex shedding. These absorbers differ by their possible rectilinear motion of the absorber mass. This is either in the direction of the pendulum axis or in perpendicular direction to it. The effectivity of both types is compared and possible realization in real devices is considered.

Miroslav Hlavacek : Synovial fluid filtration by articular cartilage with a worn-out surface zone in the human ankle joint during walking. Part I: A mathematical mixture model, pp.295-321

A mixture model of synovial fluid filtration by articular cartilage with a wornout surface zone in the human ankle joint during walking is presented for steady rolling/sliding motion. Both cartilage and synovial fluid are modelled as biphasic mixtures. While Part I of the present paper brings deduction of the governing equations, numerical results for steady pure sliding are presented in Part II. The analysis provides support for the hypothesis that if the surface zone of articular cartilage is rubbed off, a continuous synovial fluid film between the articular surfaces is not maintained in the human synovial joints of the lower extremities during walking, and that boundary lubrication might be operative in this case.

Jerzy Barglik : Influence of input material data on accuracy of thermal calculations at induction heating, pp.323-336

The paper deals with the induction heating of a thin non-ferromagnetic infinite strip located in the transverse electromagnetic field. The aim is to estimate the influence of the input physical parameters of the heated material on accuracy of the numerical calculation of the steady state temperature field distribution in the strip. Solution to the problem starts from building the mathematical models of the electromagnetic and temperature fields in moving or non-moving medium. These models are then solved by professional program OPERA 3D (electromagnetic field) supplemented with several user procedures (2D temperature field in the 3D region). The theoretical analysis is illustrated by suitable examples and discussion of their results.