Jaroslav Franek

Changes of Ni-Zn Properties by Substitution of Zn With Cu and Co Ions

The effect of partial substitutions of Zn²⁺ ions with Cu²⁺ and Co²⁺ ions in Ni_0.33Zn_0.67Fe₂O₄ ferrite were investigated on magnetic properties. Fine particles of Ni_0.33Zn_0.67-xMe_x, ferrites with Me = Cu²⁺/Co²⁺ were prepared by the self-propagated combustion method. Variation of temperature dependences of the magnetic susceptibility χ(T) with composition is discussed and possible magnetic mechanism is investigated. Grain size is one of the factors determining the magnetic properties of ferrite materials. The chemical and structural changes of ferrite during substitution treatment are analyzed also using Mossbauer spectrum and SEM. Initial permeability varies with ion content x in ferrite materials, which is attributed to the variation of grain size.

MICROWAVE ELECTROMAGNETIC FILED AND TEMPERATURE DISTRIBUTION IN A MULTILAYERED WOOD{CEMENT BOARD

Microwave Electromagnetic Filed and Temperature Distribution in a Multilayered Wood-Cement Board The aim of this work was theoretical considerations of a multi-layer structure and estimation of some properties of previously designed and prepared modified wood-cement boards. These were enriched by carbon powder as electric admixture to gain a high damping of electromagnetic radiation in microwave frequency region. The dissipated power and temperature assessment based on the heat and electromagnetic wave propagation in case of perpendicular incident radiation are presented. As a practical criteria of the shielding effectiveness —the drop of the temperature measured behind an irradiated multilayered shield was utilized.

Numerical modelling of the internal reflection and Goos-Hänchen shift of electromagnetic beam wave

Abstract Total internal reflection of plane waves is a well-known phenomenon. Some new aspects of the numerical treatment of the total internal reflection phenomena, concerning the beam-wave, are discussed.

Numerical treatment of the spatio-temporal electromagnetic beam-wave packet

Abstract Propagation of a two-dimensional spatio-temporal electromagnetic beam wave is analysed. In parabolic (paraxial) approximation the exact analytical results for a spatio-temporal Gaussian impulse can be obtained. For solution of the full wave equation the numerical simulation has to be used. The various facets of this simulation are discussed here.

ON INDUCTION HEATING -- CONDUCTOR EXCITED BY EXTERNAL FIELD

Electromagnetic field in a banded strip conductor excited by external AC voltage driven coil is analyzed. Inhomogeneous wave equation describing this axis-symmetrical configuration is deduced and solved to find the induced current density and the directional energy flux density (Poynting vector) in the conductor.