Regional trends in European induction data     

Karel Pěč  Jana Pěčová  Oldřich Praus  Reviewer M. Hvoždara 《Studia Geophysica et Geodaetica》1977,21(3-4):383-393

n ¶rt;a, n¶rt;mau 531 au ¶rt; u aum m u¶rt;uu n mumu ana¶rt;, ¶rt; u -m n, aauum ¶rt;um u u amuaa n¶rt;naa ma ua aama. uu nmam an¶rt;u ¶rt; u aum aam ¶rt;au cuu uP _n ^m , n¶rt;am mn n=1, 2, 3 u 5 (m n). u uua ¶rt;a¶rt;amu uu n¶rt;mauu uum au (a. 1) u u n aumam uu nmu, m n¶rt;mam u¶rt; am uuu ¶rt; u aum (u. 1–4). annuau 2 u 5 mn nm ma am mmmu m (u. 5, 6). ama uuu u m aam amu uu uma.  相似文献   

Dynamic loading of the boundaries in the finite-difference study of diffraction     

Jiří Zahradník  Reviewer J. Vaněk 《Studia Geophysica et Geodaetica》1977,21(3-4):255-259

Summary The finite-difference method can be used for obtaining the theoretical seismic response of a block structure to an incident plane wave. Computer time is saved by solving an equivalent problem of dynamic loading of the boundary of the block structure. The loading is performed by means of a set of discrete body forces, replacing the incident wave at the interface.  相似文献   

Magnetohydrodynamic oscillations due to precessional motion     

Jiří Trešl  Reviewer G. Siráň 《Studia Geophysica et Geodaetica》1977,21(1):27-34

Summary The motion of a non-viscous liquid medium with an ideal electrical conductivity, enclosed in the ellipsoidal cavity of an envelope subject to precessional motion, is investigated. Inside the cavity there is a toroidal magnetic field. It is proved that the precessional motion of the envelope generates forced oscillations of the medium with a period of 24 hours and two different types of eigen oscillations. Expressions for computing the amplitudes and frequencies of all types of oscillations are derived. The maximum values of disturbance fields are determined for geophysically acceptable parameters.  相似文献   

On the possibilities of studying impulsive elastic waves in an inhomogeneous medium by the finite difference method     

Jiří Zahradník  Reviewer J. Vaněk 《Studia Geophysica et Geodaetica》1974,18(4):339-358

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Book reviews     

Tlamicha  Antonín  Podolský  Jiří 《Astrophysics and Space Science》1986,120(2):307-308

Astrophysics and Space Science -  相似文献   

NLTE wind models of hot subdwarf stars     

Jiří Krtička  Jiří Kubát 《Astrophysics and Space Science》2010,329(1-2):145-150

We calculate NLTE models of stellar winds of hot compact stars (central stars of planetary nebulae and subdwarf stars). The studied range of subdwarf parameters is selected to cover a large part of these stars. The models predict the wind hydrodynamical structure and provide mass-loss rates for different abundances. Our models show that CNO elements are important drivers of subdwarf winds, especially for low-luminosity stars. We study the effect of X-rays and instabilities on these winds. Due to the line-driven wind instability, a significant part of the wind could be very hot.  相似文献   

Modelling tidal current‐induced bed shear stress and palaeocirculation in an epicontinental seaway: the Bohemian Cretaceous Basin,Central Europe     

ANDREW J. MITCHELL  DAVID ULIČNÝ  GARY J. HAMPSON  PETER A. ALLISON  GERARD J. GORMAN  MATTHEW D. PIGGOTT  MARTIN R. WELLS  CHRISTOPHER C. PAIN 《Sedimentology》2010,57(2):359-388

Lower to Middle Turonian deposits within the Bohemian Cretaceous Basin (Central Europe) consist of coarse‐grained deltaic sandstones passing distally into fine‐grained offshore sediments. Dune‐scale cross‐beds superimposed on delta‐front clinoforms indicate a vigorous basinal palaeocirculation capable of transporting coarse‐grained sand across the entire depth range of the clinoforms (ca 35 m). Bi‐directional, alongshore‐oriented, trough cross‐set axes, silt drapes and reactivation surfaces indicate tidal activity. However, the Bohemian Cretaceous Basin at this time was over a thousand kilometres from the shelf break and separated from the open ocean by a series of small islands. The presence of tidally‐influenced deposits in a setting where co‐oscillating tides are likely to have been damped down by seabed friction and blocked by emergent land masses is problematic. The Imperial College Ocean Model, a fully hydrodynamic, unstructured mesh finite element model, is used to test the hypothesis that tidal circulation in this isolated region was capable of generating the observed grain‐size distributions, bedform types and palaeocurrent orientations. The model is first validated for the prediction of bed shear stress magnitudes and sediment transport pathways against the present‐day North European shelf seas that surround the British Isles. The model predicts a microtidal to mesotidal regime for the Bohemian Cretaceous Basin across a range of sensitivity tests with elevated tidal ranges in local embayments. Funnelling associated with straits increases tidal current velocities, generating bed shear stresses that were capable of forming the sedimentary structures observed in the field. The model also predicts instantaneous bi‐directional currents with orientations comparable with those measured in the field. Overall, the Imperial College Ocean Model predicts a vigorous tide‐driven palaeocirculation within the Bohemian Cretaceous Basin that would indisputably have influenced sediment dispersal and facies distributions. Palaeocurrent vectors and sediment transport pathways however vary markedly in the different sensitivity tests. Accurate modelling of these parameters, in this instance, requires greater palaeogeographic certainty than can be extracted from the available rock record.  相似文献   

Reduction of surface subsidence risk by fly ash exploitation as filling material in deep mining areas   总被引：1，自引：1，他引：0  

Trčková Jiřina  Šperl Jan 《Natural Hazards》2010,53(2):251-258

The possibility of filling empty underground spaces, which exist owing to the extraction of mineral raw materials, with fly ash and cement fly ash mixes has been studied for the purpose of reducing the impact of deep mining on the surface. The method of physical modelling was used to study the behaviour of fly ash mixes deposited in extracted mine spaces. The models were constructed for two different geometries of underground extracted mine spaces: into cavities of the type of large slits created in the course of mining in steeply lode deposits without subsequently filling the empty space and in vertical shafts of rectangular or circular cross-section with horizontal side headings that have partly caved in due to mine shocks or other seismic events.  相似文献   

Monitoring of heat transmission from buildings into geological environment and evaluation of soil deformation consequences in foundation engineering     

Işık Yilmaz  Marian Marschalko  David Lamich  Marián Drusa  Jiří Machačík  Silvie Heviánková  Miroslav Kyncl  Eva Lacková  Iva Bestová  David Krčmář  Egon Stutz  Martin Bednárik 《Environmental Earth Sciences》2014,72(8):2947-2955

In engineering geology a number of factors affecting foundation conditions are taken into consideration during engineering-geological investigations. This article deals with the factor of heat sourced from a structure (brick kiln) as a restrictive factor in foundation engineering in clay soils and introduces a documentation of soil deformation observations as an impact of the heat transmission into the geological environment. It was carried out in Southern Moravia in the Czech Republic, where the dominant foundation soils are Neogeneous clays where differential settlements of a tunnel kiln structure occurred as a result of ignoring the boundary conditions of temperature changes in the soil environment. The brick kilns caused heterogeneous spatial changes in the subsoil temperatures. This consequently resulted in differential settlements due to temperature changes originating from the kilns. The differential settlements reached as much as 150 mm. The major objective of the article is to highlight the importance of the heat transmission from buildings into the geological environment as a factor which should be considered in engineering geology and its application in planning. A new procedure for reducing or elimination of ground movements sourced from underlying clayey soils depending on the heat changes was also suggested in this context.  相似文献   

Forcing mechanisms of a heavy precipitation event in the southeastern Adriatic area     

Branka Ivančan-Picek  Kristian Horvath  Nataša Strelec Mahović  Marjana Gajić-Čapka 《Natural Hazards》2014,72(2):1231-1252

The aim of this study was to identify the main mesoscale features and mechanisms responsible for the generation of an extreme precipitation event as a contribution to improving the modelling of processes that produce HPEs. The event occurred during the morning hours on 22 November 2010 over the Dubrovnik coast in Croatia and the hinterland mountain range of the southern Dinaric Alps and caused severe flash floods and landslides and consequent interruption of traffic and electricity supply as well as other infrastructural damage. The analysis is geographically focused on the southern portion of the eastern Adriatic region, which is prone to relatively frequent heavy precipitation events that occur mostly in autumn. This area is one of the rainiest in Europe with expected annual amounts of precipitation greater than 5,000 mm in the mountainous hinterland. The mechanisms responsible for the formation of convection were analysed using synop measurements, satellite data and numerical experiments performed with the WRF model, which was set up at the convection-permitting resolution in the innermost domain. Satellite data were used to identify the precipitation systems and to estimate the intensity of the precipitation during the period of interest. The development of the precipitation system was connected to a strong large-scale ascent over the southern Italy and southern Adriatic due to the advection of warm air and cyclonic vorticity advection, which increases with height. The numerical simulations highlighted the essential role of a southerly low-level jet stream in the transport of warm and moist air towards the affected area. The convergence of two branches of low-level marine air favoured convection triggered over the coast and sea. Furthermore, numerical sensitivity experiments suggested that the orography of the Dinaric Alps plays an essential role in the precipitation maximum over the mountainous hinterland, but also that the orography was not the crucial factor in the heavy precipitation near Dubrovnik. This study highlights the need for a dense network of observations, especially radar measurements, to validate the simulated mechanisms and improve numerical forecasts via data assimilation.  相似文献