No. 1, 1999


Ivo Dolezel, Rudolf Tesar: Protection of buried telecommunication cables against external electromagnetic influences, 1–15

Reliable protection of buried telecommunication cables against the external electromagnetic influences (particularly from near overhead lines of high and very high voltage, traction trolley lines or high voltage cable networks) is one of the necessary conditions for a correct design of corresponding cable runs. The presented paper deals with improved methodology of evaluation of these influences and possibilities of their reduction to acceptable values. Theoretical analysis is supplemented by several illustrative examples and discussion concerning the values of reduction coefficients for different kinds, materials and positions of the shielding elements.

Vratislav Kafka: Shape memory under complex loading: mesomechanical modeling, 17–33

The general author's mesomechanical concept of modeling shape memory effect is applied to deformation processes that are not uniaxial, where uniaxial loading in one direction is followed by loading in another direction. The effect of the first segment of loading and deformation is reflected in the following segment by residual microstresses. It is shown that-according to our model-recovery of strain that starts from the end of the second segment owing to heating is orientated directly to the zero deformation point and is not affected by the loading path and deformation path. This agrees with experimental observations and thus corroborates the appropriateness of our model even for complex loading.

Jan Hlina, Vaclav Nenicka, Vit Novak, Jurgen Hirschinger, Wilhelm Prettl: Diagnostics of nonlinear dynamic systems for some theoretical and experimental models with the decisive role of convection, 35–77

Basic characteristics of one theoretical and three experimental nonlinear dynamic systems were studied using several diagnostic methods. The results show some common features typical for such systems, in particular frequent transitions between many types of regular and chaotic behaviour. The experimental techniques used for the diagnostics included primarily optical methods, based on application of photodiode arrays for fast multichannel detection of the optical radiation of arcs and plasma jets and high-sensitivity camera detecting the semiconductor photoluminescence. The data yielded by all the theoretical and experimental models were investigated using various diagnostic methods, based on the fast Fourier transform including the phase relation analysis, wavelet transform and calculations of correlation dimensions. The results enabled to identify the parameters decisive for the formation of characteristic oscillation modes.

Petr Filip, Jiri David: On the flow rate and annular arrangement in the Poiseuille flow of power-law fluids, 79–86

The paper aims at the determination of dependence of flow rate on the geometrical arrangement of doubly connected annular region in the case of the steady axial Poiseuille flow of power-law fluids. In the following the assumption of a constant pressure gradient is made. Fluid area of the annular regions (with varying radii) is supposed to be of the same cross-sectional area. As a result the relation between flow rates for different doubly connected annular regions is obtained in a simple analytical form depending only on two kinds of parameters: aspect ratios of the individual radii and flow behaviour index n. This relation enables easy determination of possible enhancement of flow rate through annular passages.

Onkar Nath, S.N. Ojha, H.S. Takhar: Propagation of a shock wave in a rotating interplanetary atmosphere with increasing energy, 87–98

A self-similar model of a spherically symmetric shock wave propagation, driven by a flare release in a non-uniform rotating atmosphere, has been considered. The total energy content of the model is assumed to increase with time within the inner expanding surface and the shock front. The variation of flow velocity, rotation, pressure, density and energy behind the shock wave have been discussed. The variation of the flow variables, with and without rotation, have been compared.