On causality in dynamic response analysis by time-dependent boundary element methods

The ramifications of a particular type of causality constraint, namely so-called shadow-zones, are explored in the context of time-dependent boundary element methods. In particular, wave propagation problems in 2-D elastic soil media with a non-convex shape are analysed.     

Solar limb darkening 1986–1990 (λλ303 to 1099 nm)

The Sun's limb darkening was observed repeatedly between the 1986 minimum and the 1990 maximum of solar activity.Systematic variations, which could depend either on the momentary activity and/or the phase in the solar cycle, werenot detectable, either at continuum wavelengths or in two broad-band spectral intervals. Completelyirregular variations, which concern not only individual, successive scans (due to granulation, etc.), but also thedaily andseasonal averages, are usually less than 1%, but can reach occasionally 2% or even more. Minoreast-west asymmetries even in the seasonal means seem to be well established, mainly for < 400 nm. Thefinal, mean limb-darkening coefficients agree basically with those published by Pierce and Slaughter (1977) and Pierce, Slaughter, and Weinberger (1977), but show a much lower scatter when plotted against wavelength.     

Laboratory testing and numerical simulation of properties and thermal-induced cracking of Eibenstock granite at elevated temperatures

The knowledge about thermo-mechanical properties of granite is still limited to some extent. Individual measurements are necessary to obtain reliable properties for specific granite types. A reliable numerical model of thermal cracking behaviours of granite exposed to extreme high temperatures (e.g. 800–1000 °C) is missing. In this study, the impact of temperature up to 1000 °C on physical, mechanical, and thermal properties as well as thermo-mechanical coupled behaviour of Eibenstock granite was investigated by laboratory testing and numerical simulations. The physical properties including mineral composition, density, P-wave velocity, and open porosity are measured to be temperature dependent. Uniaxial compression and Brazilian tests were carried out to measure uniaxial compressive strength (UCS), Young’s modulus, stress–strain relationship, and tensile strength of Eibenstock granite before and after thermal treatment, respectively. Thermal properties including specific heat, thermal conductivity, thermal diffusivity, and linear thermal expansion coefficient are also measured and found to be temperature dependent, especially the expansion coefficient which shows a steep increase around 573 °C as well as at 870 °C. The numerical simulation code FLAC^3D was used to develop a numerical scheme to simulate the thermal-induced damage of granite at high temperatures. Statistical methods combined with real mineral composition were used to characterize the heterogeneity of granite. The numerical model is featured with reliable temperature-dependent parameters obtained from laboratory tests. It can well reproduce the laboratory results in form of thermal-induced micro- and macrocracks, as well as the stress–strain behaviour and the final failure pattern of Eibenstock granite after elevated temperatures up to 1000 °C. The simulation results also reveal that the thermal-induced microcracks are randomly distributed across the whole sample. Although most thermal-induced damages are tensile failures, shear failure begins to develop quickly after 500 °C. The obvious UCS reduction in granite due to heating is mainly caused by the increase in shear failure. The simulation also shows that the dominant impact of α–β quartz transition is widening pre-existing cracks rather than the formation of new microcracks.

     

Numerical modeling to investigate slopes and mass flow phenomena

An overview is given about up-to-date techniques for slope stability and deformation analysis as well as mass flow phenomena simulation. The paper concentrates on a few aspects in respect to the use of numerical modeling techniques, especially in relation to the shear strength reduction techniques, discontinuum modeling, probabilistic concepts, the combination of GIS and numerical modeling as well as sophisticated hydro-mechanical coupling with time-dependent material behavior. At present these topics are preferred topics of scientific and technical research.     

Standardization of vulnerability maps

Groundwater vulnerability assessment schemes are used for the estimation of potential groundwater contamination at different scales and on different administrative levels. However, the term vulnerability is not standardized and the available methods are not able to give a unique assessment of vulnerability creating thus uncertainty in the interpretation and in further application concerning decision creation processes. To judge the information of vulnerability maps certainly and to value the general trends of vulnerability assessment of different methods, four different vulnerability methods of the parametric system group have been applied on a karst area in southwestern Germany to perform a comparative assessment and correlation of these vulnerability assessment methods, namely DRASTIC, PI, EPIK, and GLA. It is shown that by means of simple statistical considerations the first highly different vulnerability maps could be made more coherent after reclassification. The reclassified vulnerability assessments show a more consistent vulnerability distribution pattern and provide the possibility of area-wide validation of the maps as the chosen vulnerability classification is theoretically connected to the mean transit time of percolation water and is largely independent of the applied vulnerability assessment method.     

Der Granit von Plöcking (Typus Mauthausen) aus dem oberösterreichischen Mühlviertel.

Ohne ZusammenfassungMit 3 Textabbildungen     

Baustil und Regionalmetamorphose im präkambrischen Grundgebirge Brasiliens

Ohne ZusammenfassungMit 2 Karten, 4 Profilen und 2 TextabbildungenHerrn Prof. Dr.K. H. Scheumann zum 80. Geburtstag gewidmet.     

Analytical Reference Functions <Emphasis Type="Italic">F</Emphasis>(λ) for the Sun's Limb Darkening and Its Absolute Continuum Intensities (λλ 300 to 1100 m)

It is shown (1) that the coefficients A_i of the limb darkening functions I(μ)/I_center = P₅ (μ) = ∑A_i μⁱ (i = 0... 5; μ = cos ϑ), which had been published by Neckel and Labs (Solar Phys. 153, 91, 1994), can well be approximated by analytical functions of wavelength λ, and (2) that at first sight purely formal extrapolation of the functions P₅(μ) to the very limb (μ = 0.0) is not meaningless: in combination with absolute intensities for the disk center these functions yield ‘limb intensities’ which all correspond to almost the same ‘limb temperature’, T_limb≈4746 K. Together these results lead to ‘reference functions’ which can quickly yield rather reliable values of the Sun's continuum intensities, for any values of μ and λ.