Neuere veröffentlichungen     

Erich Pansch  Fritz Holzkamm  Dietrich Voppel 《Ocean Dynamics》1983,36(4):167-170

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Relation between flow,surface‐layer armoring and sediment transport in gravel‐bed rivers     

John Pitlick  Erich R. Mueller  Catalina Segura  Robert Cress  Margaret Torizzo 《地球表面变化过程与地形》2008,33(8):1192-1209

This study investigates trends in bed surface and substrate grain sizes in relation to reach‐scale hydraulics using data from more than 100 gravel‐bed stream reaches in Colorado and Utah. Collocated measurements of surface and substrate sediment, bankfull channel geometry and channel slope are used to examine relations between reach‐average shear stress and bed sediment grain size. Slopes at the study sites range from 0·0003 to 0·07; bankfull depths range from 0·2 to 5 m and bankfull widths range from 2 to 200 m. The data show that there is much less variation in the median grain size of the substrate, D_50s, than there is in the median grain size of the surface, D₅₀; the ratio of D₅₀ to D_50s thus decreases from about four in headwater reaches with high shear stress to less than two in downstream reaches with low shear stress. Similar trends are observed in an independent data set obtained from measurements in gravel‐bed streams in Idaho. A conceptual quantitative model is developed on the basis of these observations to track differences in bed load transport through an idealized stream system. The results of the transport model suggest that downstream trends in total bed load flux may vary appreciably, depending on the assumed relation between surface and substrate grain sizes. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

New Apparatus and Experimental Setup for Long-Term Swelling Tests on Sulphatic Claystones     

Erich Pimentel  Georg Anagnostou 《Rock Mechanics and Rock Engineering》2013,46(6):1271-1285

An apparatus and experimental setup were developed to carry out a series of extremely slow and long-lasting swelling, creep or chemo-mechanics tests simultaneously. The equipment was designed specifically for investigating the behaviour of sulphatic claystones. The tests will take at least 10–15 years to complete and will provide unprecedented information about the so-called swelling law, i.e. the relationship between swelling strain and swelling stress. The swelling law is very important for designing tunnels in swelling rock. Our knowledge of the swelling law, however, is only sufficiently reliable with respect to claystones without anhydrite (e.g. marls, opalinus clay). The swelling law for sulphatic claystones remains unknown, even in qualitative terms. This is due to the underlying physico-chemical mechanisms, which are fundamentally different from those of purely argillaceous rocks. Another reason is the extremely long duration of the swelling process of clay-sulphate rocks, which makes systematic field or laboratory investigations very difficult. In order to close this knowledge gap, a series of 25 long-term simultaneous swelling tests has been started.  相似文献   

Numerical simulation of the effect of interface friction of a bounding structure on shear deformation in a granular soil     

Babak Ebrahimian  Erich Bauer 《国际地质力学数值与分析法杂志》2012,36(12):1486-1506

Recently, the shear behavior of a cohesionless granular strip that is in contact with a very rough surface of a moving bounding structure has been numerically investigated by several authors by using a micropolar hypoplastic continuum model. It was shown that the micropolar boundary conditions assumed along the interface have a strong influence on the deformations within the granular layer. In previous investigations, only interface friction angles for very rough bounding structures were assumed. In contrast, the focus of the present paper is on the influence of the interface roughness on the deformation behavior of the granular strip when the interface friction angle is lower than the peak friction angle of the granular material. In addition to the interface friction angle, particular attention is also paid to the influence of the mean grain diameter, the solid hardness, the initial void ratio, and the vertical stress on the maximum horizontal shear displacement within the granular layer before sliding is started. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   

Characterization of Navajo Sandstone concretions: Mars comparison and criteria for distinguishing diagenetic origins     

Sally L Potter  Marjorie A. Chan  Erich U. Petersen  M. Darby Dyar  Elizabeth Sklute 《Earth and Planetary Science Letters》2011,301(3-4):444-456

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On the efficiency of horizontal diffusion and numerical filtering in an Arakawa‐type model     

Erich Roeckner  Hans V. Storch 《大气与海洋》2013,51(3):239-253

Abstract

In a series of 5‐day forecasts with a 3‐layer/2.8° hemispheric model, horizontal diffusion schemes of the second and fourth degree are compared with a numericalfilter technique. The results, which are discussed mainly in terms of spectral energetics in zonal wavenumber space, indicate that fourth‐degree diffusion is more scale selective than second‐degree and equivalent to filtering. The seventh‐order filter applied only intermittently to the prognostic variables is superior to fourth‐degree diffusion from the viewpoint of computational economy. Excessive dissipation of the long waves may inhibit the production of eddy kinetic energy from eddy available potential energy.  相似文献   

Factors driving the biogeochemical budget of the Amazon River and its statistical modelling     

Vincent Bustillo  Reynaldo Luiz Victoria  Jose Mauro Sousa de Moura  Daniel de Castro Victoria  Andre Marcondes Andrade Toledo  Erich Collicchio 《Comptes Rendus Geoscience》2011,343(4):261-277

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Sizes, shapes, and albedos of the inner satellites of Neptune     

Erich Karkoschka 《Icarus》2003,162(2):400-407

Based on 87 resolved Voyager images of the five innermost satellites of Neptune, their shapes were measured and fit by tri-axial ellipsoids with the semi-axes of 48 × 30 × 26 km for Naiad, 54 × 50 × 26 km for Thalassa, 90 × 74 × 64 km for Despina, 102 × 92 × 72 km for Galatea, and 108 × 102 × 84 km for Larissa. Thomas and Veverka published a similar shape for Larissa (104 × 89 km, J. Geophys. Res. 96, 19261-19268, 1991). The other satellites had no published shapes. Using Voyager photometry of the six inner satellites by the same authors and the revised sizes, including the published size of Proteus, the reflectivity within this inner system was found to vary by about 30%. Geometric albedos in the visible are estimated between 0.07 for Naiad and 0.10 for Proteus. The rotational lightcurves of these satellites seem to be due to satellite shapes.  相似文献   

Zur weiteren Kennzeichnung der Grüngesterne in der Bernsteiner Zone der Rechnitzer Serie     

Dr. A. Erich 《Mineralogy and Petrology》1966,11(1-2):93-120

Ohne ZusammenfassungMit 10 TextabbildungenHerrn Prof. DDR.H. Wieseneder danke ich für die Aufnahme des größten Teiles der Mikrolichtbilder.  相似文献   

An improved sealing system for triaxial sample columns     

Ted Koczynski  Erich Scholz 《Pure and Applied Geophysics》1993,141(2-4):653-657

A new method for making gas-tight seals for moderate temperature duty on triaxial deformation apparatus sample columns is described. This includes the modification of the piston and closure plug to enable rapid and inexpensive changes to the loading column.  相似文献