Design criteria for roadway supports to resist dynamic loads

Summary Conditions under which dynamic loads occur in mines are briefly described and the special vulnerability of roadways in coal mines to fail under dynamic load is considered. A method for assessment of shock load energy anticipated is proposed, based on the volume of rock and the velocity of rock particles induced by rapid rock failure and/or seismic tremors. Case examples from Upper Silesian coal mines are given and the safety factor of steel supports against the shock energy from rockbursts is discussed. The shock energy damping ability of various parts of steel supports and support systems is calculated as a basis for rational support design. Results of six mine experiments where various types of roadway support were installed and then loaded dynamically by blasting within surrounding rocks are discussed.     

Intensity of vlf and elf phenomena in the outer ionosphere

Summary Spatial and temporal variability of natural ELF-VLF phenomena field intensity has been studied using data from Interkosmos satellites with apogees below 2000 km. The results show a distinct dependence of the diurnal variation and latitudinal intensity distribution on the magnetic activity. The L-value at which the maximum of plasmaspheric noise occurs, e.g., correlates better with the Dst-index than with other indicies.

---

mama u a auau anmu n mm - u a ua a uu ¶rt;a uu m an u 2000 . mam naam m auum m ¶rt;a u um an¶rt;u uu m aum amumu. uua L-naama, a m nm au naa uu, um Dst-u¶rt; ¶rt;uu u¶rt;auaum amumu.

     

A Lower Palaeozoic shallow water sequence in the eastern European Variscides (SW Poland): provenance and depositional history

The Gackowa Formation of inferred Cambrian —Ordovician age is part of the metamorphosed pre-Variscan basement of the southern Kaczawa Mountains of the Sudetes region, south-west Poland. Previously variously interpreted as lavas, tuffs and sandstones, it is shown to consist of about 200 m of originally well-sorted siliclastic sedimentary rocks within a sequence of predominantly mafic volcanic rocks. Four facies have been distinguished based on relict sedimentary structures and textures and these suggest that deposition took place on a storm-dominated shelf, mostly above the wave base. The petrography, detrital zircon morphologies and geochemistry suggest affinity with, and derivation in large part from, acid volcanic rocks at a comparable stratigraphic position in a separate tectonostratigraphic unit to the south. The Gackowa Formation and its acid volcanic source rocks have a clear continental geochemical signature, in contrast with the mantle-derived basic/bimodal volcanic rocks below and above; it is suggested that the parent acid magma originated by crustal melting during the ascent of these mantle-derived magmas. A continental crust setting is inferred for the deposition of the Gackowa Formation sandstones, thus suggesting a continental setting for the associated within-plate basalts. The entire volcanic/sedimentary succession resembles elements of the Lower Palaeozoic of Germany, and all may have formed in an initial rift setting during Late Precambrian to Ordovician times.     

Keplerian expansions in terms of Henrard's practical variables

Formulae for the Keplerian expansions in terms of Henrard's practical variables are given. Two different methods were applied: one using the Bessel functions and one based on the Lie transforms. The former involves less series products, but the latter is more flexible and universal.     

The efficiency of gravitational diffusion for the separation of elements in the prestellar gas

The gravitational separation of iron atoms with respect to hydrogen is evaluated by simple models of globular clusters and spherical galaxies before star formation, as well as in a column of gas perpendicular to the galactic plane in the solar neighborhood. The changes of the iron abundance are small, but qualitatively consistent with the observed facts: (1) there is a positive correlation between the mass number of the element and the steepness of its abundance gradient; (2) there is a connection between the mass and the density concentration of the globular clusters and their chemical composition; (3) the changes of the chemical content in the galactic plane are very small during the life of the galactic disk, but are increasingly significant in the upper layers.     

Static spherical configurations of cold matter in the Einstein-Cartan theory of gravitation

We investigate static, spherical configurations of cold catalized matter in the Einstein-Cartan theory of gravitation. Assuming that density of spin is proportional to the number density of baryonsn and using an equation of state of a degenerate, relativistic Fermi gas, we numerically integrated the relativistic equation of equilibrium. We have also studied the stability of those configurations. Configurations with central number densityn _c such that where is the effective pressure, are very similar to general relativistic configurations with the same central density. In the Einstein-Cartan theory there exists another disjoint family of equilibrium configurations for which but . Those configurations have very small masses 10^–6 g and raddi 10^–34 cm and are unstable.Supported in part by Research Grant MR-I-7.     

Comparison of Two Wavelet Transform Coherence and Cross-Covariance Functions Applied on Polar Motion and Atmospheric Excitation

The wavelet transform techniques were applied to compute time-frequency spectra, coherence and cross-covariance functions between complex-valued polar motion and atmospheric excitation functions. These wavelet transform approaches are based on the classical wavelet transform with Morlet wavelet and the harmonic wavelet transform. The computed coherence and cross-covariance functions enable comparison of polar motion and atmospheric excitation functions data in the chosen frequency band. In the study we concentrate on short period oscillations with periods ranging from several to about 250 days. The time lag functions show frequency dependent time lags corresponding to maxima of the modules of cross-covariance functions between the polar motion and atmospheric excitation functions.