A note on the generation of periodic granular microstructures based on grain size distributions     

H. A. Meier  E. Kuhl  P. Steinmann 《国际地质力学数值与分析法杂志》2008,32(5):509-522

This short communication discusses an algorithm suited for the generation of periodic microstructures of granular media. Its particular features are a user‐defined grain size distribution, a representative volume element which is intrinsically periodic ab initio and a user‐defined termination criterion, controlled by an increase of volume fraction. For low densities our particle packings resemble fluids or gases, while we aim to reach for rather dense particle packings, similar to granular solids. The generated microstructures can thus be readily incorporated into large multiscale simulations, e.g. on the integration point level of a finite element analysis of a particular sand or concrete. The individual grain size distribution of the granular medium is incorporated through the introduction of different growth rates governing the final particle size distribution. We briefly sketch the generation of the representative volume element within a serial event‐driven scheme and demonstrate how periodic boundary conditions are ensured throughout the representative volume element generation process. The potential of the suggested algorithm will be illustrated through the generation of two different periodic multi‐disperse microstructures. They are based on different given grain size distributions, one for a quartz sand with a low non‐uniformity index and one for concrete aggregates classified as A32 by the German standard norm DIN 1045 to have a rather large variation in grain size. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Identification of estrogen-like alkylphenols in produced water from offshore oil installations   总被引：1，自引：0，他引：1  

Boitsov S  Mjøs SA  Meier S 《Marine environmental research》2007,64(5):651-665

Produced water released into the sea from oil installations contains a vast number of organic compounds. This work focuses on the analysis and identification of phenols in produced water, in particular long-chain para-substituted alkylphenols, which act as endocrine disruptors for marine biota. Some alkylphenol standards, unavailable commercially, have been synthesised and some compounds of interest identified. However, a complete identification is not possible since conventional GC techniques cannot achieve the desired degree of separation. An overview of the levels of the 52 known alkylphenols in produced water from nine oil installations in the North and Norwegian Seas has been made. The previously unidentified alkylphenols in produced water have been characterised by means of alkylphenol retention indices (APRI) and mass spectrometry, and their total amounts estimated for the same nine locations. Our results confirm the presence of naphthols and other as yet unidentified compounds in produced water, while thiophenols were not detected by the used technique.  相似文献   

Anomalous gold, antimony, arsenic, and tungsten in ground water and alluvium around disseminated gold deposits along the Getchell Trend, Humboldt County, Nevada     

David J. Grimes  Walter H. Ficklin  Allen L. Meier  John B. Mchugh 《Journal of Geochemical Exploration》1995,52(3)

Ground-water, alluvium, and bedrock samples were collected from drill holes near the Chimney Creek, Preble, Summer Camp, and Rabbit Creek disseminated gold deposits in northern Nevada to determine if Au and ore-related metals, such as As, Sb, and W, are being hydromorphically mobilized from buried mineralized rock, and, if they are, to determine whether the metal-enriched ground water is reacting with the alluvial material to produce a geochemical anomaly within the overburden.Results of chemical analyses of drill-hole water samples show the presence of hydromorphic dispersion anomalies of Au, As, Sb, and W in the local ground-water systems associated with these deposits. Background concentrations for Au in the ground water up-gradient from the buried deposits was less than 1 nanogram per liter (ng/L), near the deposits the Au values ranged from 1 to 140 ng/ L, and in drill holes penetrating mineralized rock, concentrations of Au in the ground water were as high as 4700 ng/L. Highest concentrations of Au were found in ground-water samples where the measured E_h and the distribution of arsenic species, arsenite [As(III)] and arsenate [As(V)], indicated oxidizing redox potentials. Similarly, As, Sb, and W concentrations in the ground water near the deposits were significantly enriched relative to concentrations in the ground water up-gradient from the deposits. In general, however, the highest concentrations of As, Sb, and W occurred in ground-water samples where the measured E_h and the distribution of arsenic species indicated reducing conditions. Arsenic concentrations ranged from 9 to 710 micrograms per liter (μg/L); Sb, from less than 0.1 to 250 μg/L; and W, from 1 to 260 μg/L.In addition, analysis of sequential dissolution and extraction solutions of drill cuttings of alluvium and bedrock indicate geochemical anomalies of gold and ore-related metals in the overburden at depths corresponding to the location of the present-day water table. This relationship suggests that water-rock reactions around these buried deposits are active and that this information could be very useful in exploration programs for concealed disseminated gold deposits.  相似文献   

Buchbesprechungen     

H. Ambühl  Bührer  K. Hertelendy  Rudolf Koblet  J. Zeller  M. Meier  Pius Stadelmann 《Aquatic Sciences - Research Across Boundaries》1971,33(2):601-607

Ohne Zusammenfassung  相似文献   

Die Ausaperung der Schneedecke in Abhängigkeit von Strahlung und Relief     

R. Meier  B. Schädler 《Theoretical and Applied Climatology》1979,27(2-3):151-158

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Lithospheric structure in the area of Crete constrained by receiver functions and dispersion analysis of Rayleigh phase velocities   总被引：2，自引：0，他引：2  

B. Endrun  T. Meier  M. Bischoff  H.-P. Harjes 《Geophysical Journal International》2004,158(2):592-608

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Two-point statistics of vertical crustal movements of the Pannonian basin     

S. Meier 《Journal of Geodynamics》1987,8(2-4)

The Pannonian Basin or in a broad sense, the Carpatho-Balkan region, is a suitable test area to study the statistical qualities of the Earth's vertical crustal movements. The second-order moments of relative and absolute quantities of motion (vertical velocity, horizontal gradient) are given for the type of a subsiding region with uplifts in its marginal zone — in the ideal case of circular ssymetry. The foundation is the theory of two-dimensional homogenous stochastic processes. Empirically estimated autocovariance functions of the relative vertical rate are approximated by model functions, corresponding to the geotectonic situation of the region, and they are transformed into the wave-number domain. All modelled and empirically estimated second-order moments are given as auxiliary means for signal prediction. The properties of the signal, represented in the maps of the Earth's vertical crustal movements (1:2 500 000, Moscow 1973; 1:2 000 000, Joó et al., 1979), can be derived from the spectral representation.  相似文献   

Assessing streams in Germany with benthic invertebrates: Development of a multimetric invertebrate based assessment system   总被引：3，自引：0，他引：3  

Jürgen Bhmer  Claudia Rawer-Jost  Armin Zenker  Carolin Meier  Christian K. Feld  Regina Biss  Daniel Hering 《Limnologica》2004,34(4):416-432

The main aim of the study was to develop a multimetric assessment system for macroinvertebrate communities of small and mid-sized streams in Germany in accordance with the Water Framework Directive of the European Union. The system should be applicable by water authorities, capable of distinguishing between different impacts, and specifically adapted to all types of small and mid-sized rivers in Germany. An assessment system has been developed consisting of two modules based on the established indices for saprobic degradation and acidity, and a third module covering general degradation. For the third module a new multimetric index (MMI) was developed and tested using preclassifications for stream hydromorphological degradation, land use and general impairment as impact measures. More information on sampling method, season and the type of dominating human impairment allowed to further analyse the index' capabilities and sensitivity. It performed well in all seasons and detected all types of impairment except acidity. The usefulness of the impact measures used in this study is discussed with regard to the development of a multimetric index. The comparison of the new index with other indices showed that it is especially sensitive in detecting macroinvertebrate community responses to hydromorphological degradation and pollution such as the German AQEM index, while IBI 12 and Renkonen's similarity more reflect general community shifts caused by any type of disturbance. The new assessment system will be proposed for future use by state agencies for nationwide monitoring in the context of the Water Framework Directive implementation.  相似文献   

Magnetic phase diagrams of Mg-, Fe-, (Cu + Ti)- and Cu-substituted braunite Mn<Superscript>2+</Superscript>Mn<Subscript>6</Subscript><Superscript>3+</Superscript>SiO<Subscript>12</Subscript>     

I. Abs-Wurmbach  S. Ohmann  K. Westerholt  Th. Meier  P. Mouron  J. Choisnet 《Physics and Chemistry of Minerals》2002,29(4):280-290

 The magnetic behavior of the Jahn-Teller structure braunite, (Mn²⁺ _1−yM _y )(Mn³⁺ _{6− x} M_x)SiO₁₂, is strongly influenced by the incorporation of elements substituting manganese. Magnetic properties of well-defined synthetic samples were investigated in dependence on the composition. The final results are presented in magnetic phase diagrams. To derive the necessary data, ac susceptibility and magnetization of braunites with the substitutional elements M = Mg, Fe, (Cu+Ti) and Cu were measured. Whereas the antiferromagnetic ordering temperature, T _N , of pure braunite is hardly affected by the substitution of nonmagnetic Mg, it is rapidly suppressed by the substitution of magnetic atoms at the Mn positions. Typically for a concentration (x, y) ≥ 0.7 of the substituted elements, a spin glass phase occurs in the magnetic phase diagrams. Additionally, for the braunite system with Fe³⁺ substitutions, we observe in the concentration range 0.2 < x< 0.7 a double transition from the paramagnetic state, first to the antiferromagnetic state, followed by a transition to a spin glass state at lower temperatures. The unusual change of the magnetic properties with magnetic substitution at the Mn positions is attributed to the peculiar antiferromagnetic structure of braunite, which has been resolved recently. Received: 19 April 2001 / Accepted: 6 September 2001  相似文献   

Comparison of gravimetric and seismic constraints on the structure of the Aegean lithosphere in the forearc of the Hellenic subduction zone in the area of Crete     

K. Snopek  T. Meier  B. Endrun  M. Bohnhoff  U. Casten 《Journal of Geodynamics》2007,44(3-5):173-185

The island of Crete is located in the forearc of the Hellenic subduction zone, where the African lithospheric plate is subducting beneath the Eurasian one. The depth of the plate contact as well as the internal structure of the Aegean plate in the area of Crete have been a matter of debate. In this study, seismic constrains obtained by wide-angle seismic, receiver function and surface wave studies are discussed and compared to a 3D density model of the region.The interface between the Aegean continental lithosphere and the African one is located at a depth of about 50 km below Crete. According to seismic studies, the Aegean lithosphere in the area of Crete is characterised by strong lateral, arc–parallel heterogeneity. An about 30 km thick Aegean crust is found in central Crete with a density of about 2850 kg/m³ for the lower Aegean continental crust and a density of about 3300 kg/m³ for the mantle wedge between the Aegean crust and the African lithosphere. For the deeper crust in the area of western Crete two alternative models have been proposed by seismic studies. One with an about 35 km thick crust and another one with crustal velocities down to the plate contact. A grid search is performed to test the consistency of these models with gravimetric constraints. For western Crete a model with a thick lower Aegean crust and a density of about 2950 kg/m³ is favoured. The inferred density of the lower Aegean crust in the area of Crete correlates well with S-wave velocities obtained by surface wave studies.Based on the 3D density model, the weight of the Aegean lithosphere is estimated along an E–W oriented profile in the area of Crete. Low weights are found for the region of western Crete.  相似文献