Well modeling and estimation of hydraulic parameters     

Stephan Schumacher  Marián Slodička  Uwe Jaekel 《Computational Geosciences》1997,1(3-4):317-331

A general model for time‐dependent saturated–unsaturated waterflow caused by a single well with a given radius is presented. The storage capacity of the well tube is taken into account. The inflow into the well (with drainage) is modeled using the Signorini boundary condition. The nonconforming mixed finite element method on a multilevel adaptive grid is used for the solution of the radial symmetric, time dependent problem. Finally, van Genuchten parameters of an aquifer are determined from field measurements by inverse computations.  相似文献   

Crystal structures of iron bearing tetrahedrite and tennantite at 25 and 250°C by means of Rietveld refinement of synchrotron data     

Karen Friese  Andrzej Grzechnik  Emil Makovicky  Tonči Balić-Žunić  Sven Karup-Møller 《Physics and Chemistry of Minerals》2008,35(8):455-465

Rietveld refinement of X-ray synchrotron data was performed for two synthetic tetrahedrite samples, with 0.61 and 1.83 Fe atoms, and two synthetic tennantite samples with 0.10 and 1.23 Fe atoms p.f.u. M₁₂(Sb,As)₄S₁₃. Measurements were performed at 25 and 250°C. For both the phases, increased Fe substitution is reflected in the increased tetrahedral ‘Cu1’–S distance (‘Cu1’ is a site of Fe substitution) and Cu2–S distances. Cu2 was refined as a split position; the Cu2–Cu2 split about the plane of the S1₂S2 triangle is about 0.56 and 0.65 Å for tetrahedrite and tennantite, respectively. Cu2–Cu2 distances in the structure cavity are 2.8–2.9 Å. Between 25 and 250°C, the lattice parameter a increased by 0.02–0.04 Å and the interatomic distances by 0.01 Å on an average. Thermal expansion coefficients of little-substituted samples are similar to those of unsubstituted samples, whereas thermal expansion appears to decrease with increasing substitution by Fe. The Cu2–Cu2 split increases at 250°C by about 0.1 Å for tetrahedrite and by more than 0.15 Å for tennantite but the cage expansion is minimal so that the Cu2–Cu2 distances in the cavity decrease with temperature. Difference Fourier maps indicate that there is little residual electron density left between the two Cu2 half-sites in tetrahedrite but this inter-site density is substantially higher in tennantite. It increases with temperature, especially in the little-substituted tennantite sample.  相似文献   

Correlation Analysis of the Ultrasonic Emission from Loaded Rock Samples – the Study of Interaction of Microcracking Nucleation Centres     

J. Vilhelm  V. Rudajev  T. Lokajíček  J. Veverka 《Rock Mechanics and Rock Engineering》2008,41(5):695-714

Summary.  The locations of fractures within loaded rock samples are distributed irregularly because of the presence of inhomogeneities in the rock sample, the existence of primary microcracks and non-uniformly distributed stress. In the case of brittle fracture, the positions of these fractures can be determined by locating the foci of ultrasonic events that occur during fracturing. In some cases, the foci cluster into clouds that are restricted spatially and are referred to as nucleation centres. The purpose of this research was to determine the mutual relationship between the various nucleation centres, by cross-correlating the time-series of ultrasonic events produced by microcracking in the individual, separate nucleation centres. An additional goal was to assess the effect of the existence of such nucleation centres on the autocorrelation parameters. This study showed that the separate nucleation centres did not appear to influence one another even during the final stages of fracturing. Until now, autocorrelation analysis of acoustic emission time sequences has been applied to evaluate the mutual influence of individual events that occur in the whole sample volume, regardless of their location. In a previous study, it was found that before the total fracturing of the sample, the autocorrelation parameters changed significantly due to the increase in mutual relationship between successive events. In this study the separated nucleation centres determined by locating the ultrasonic events were subjected to autocorrelation analysis. It was demonstrated that, in the case of critical loading of the sample, the mutual influence between the events of a given nucleation centre can be observed. The experiments have demonstrated that the autocorrelation has a precursory nature and have shown that there is a significant difference in the autocorrelation parameters calculated between the set of all recorded events, and the specific sub-set. These differences must be taken into account when applying statistical predictions, for example, in the study of rock bursts. Author’s address: Jan Vilhelm, Charles University in Prague, Albertov 6, 128 43 Prague, Czech Republic  相似文献   

Short Note: Strain invariants     

Petr Vaníček  Erik W. Grafarend  Mustafa Berber 《Journal of Geodesy》2008,82(4-5):263-268

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Weather and traffic accidents in the Czech Republic, 1979–2020     

Brázdil  Rudolf  Chromá  Kateřina  Zahradníček  Pavel  Dobrovolný  Petr  Dolák  Lukáš 《Theoretical and Applied Climatology》2022,149(1-2):153-167

Theoretical and Applied Climatology - Police records, kept in the form of yearbooks, enabled analysis of the possible relationships between traffic accidents and the weather in the Czech Republic...  相似文献   

Model studies of an open-pit mine bottom loaded by artesian water pressure     

J. Trčková 《Environmental Geology》1998,35(4):245-250

 Experimental modelling methods are used for prediction of deformation and groundwater outflows at the bottom of an open-pit mine during the excavation of brown coal. Thermal gas-bearing artesian water exerts an uplift pressure on the impervious subsoil of the coal seam and threatens the stability of the mine bottom. The breakthrough of the mine bottom would seriously affect the groundwater regime and may endanger mining activities. The mining is carried out within the protection zones of the Carlsbad spa springs. Results of model studies are used to determine protective hydrogeological and mining measures for providing the maximum protection for the open-pit mine and the spa springs. Received: 16 August 1996 · Accepted: 9 June 1997  相似文献   

The significance of spatial curvature for energy output of remote quasars     

Jaroslav Souček 《Astrophysics and Space Science》1987,137(2):347-356

There is a brightening effect of quasar outputs due to the positive curvature of space in the static Universe, if we use the right expression of distance as an arc³r=R , and not the corrected luminosity distance ofr=Rsin.  相似文献   

The specific physical character of the expansion of the Universe     

Pavel Voráček 《Astrophysics and Space Science》1985,111(1):103-121

In some few steps a model describing the physical character of the cosmological expansion of the Friedmann-Robertson-Walker closed universe is developed. Due to the fact that the rate of the cosmic time is changing, the conclusion is drawn that a hidden expansion is superposed on the generally known expansion of the Universe. The resulting picture-the bi-expansive model-is brought into connection with the voids in the Universe.The expansion is described as a motion in a spatial dimension orthogonal to our space-the 4-dimensional sphere, and some characteristic properties of such a motion, compatible with the special and general relativity, are outlined. The question of the world-force retarding the expansion is touched upon, and the concepts of contemporaneity and distance in cosmology are specified. Some attempts to a physical explanation of the connection between the voids and the bi-expansive model are given in the Appendix. Also in the Appendix the Friedmann equation is rather unconventionally used for a deduction of the value of the Hubble constant as a function of distance.  相似文献   

On the origin of rotation of a celestial body     

V. A. Vujičić 《Celestial Mechanics and Dynamical Astronomy》1988,44(1-2):45-48

The differential equations of the self-rotation of a celestial body have been evaluated. From an integral of these equations a formula for angular velocity of the celestial body was obtained. This formula after being applied to the rotation of the Sun and of the Earth gives, respectively, the following angular velocity ranges: 0.588×10^–6<<18, 187×10^–6 and 0.7533×10^–5<<12,4266×10^–5. These are up to three times narrower than those previously obtained by Savi and Kaanin [1].  相似文献   

Total water content thresholds for shallow landslides,Outer Western Carpathians     

Michal Bíl  Richard Andrášik  Pavel Zahradníček  Jan Kubeček  Jiří Sedoník  Petr Štěpánek 《Landslides》2016,13(2):337-347

Shallow landslides are fairly frequent natural processes which emerge as a result of both rainfall and rapid snowmelt in the Flysch Belt of the Outer Western Carpathians. We estimated the total water content thresholds for the previously defined seven phases of increased landsliding which took place between 1939 and 2010 around the Napajedla meteorological station. The time series were reconstructed on the basis of data from surrounding stations. Rainfalls with the highest intensities (>1 mm/min) were removed from the set. Rainfall of such an intensity primarily causes overland flow and soil erosion and does not contribute to landslide threshold. The snow water equivalent was computed on the basis of the snow height, and possible errors were evaluated as interval estimations. An interval of 10 days before a landslide phase was selected for the total water content threshold. The resulting lower boundary (67.0 mm/10 days) and upper boundary (163.3 mm/10 days) thresholds of water infiltrated into soil during an event shall be part of the prepared online warning system in this area.  相似文献