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431.
Pooja Mahapatra Hans van der Marel Freek van Leijen Sami Samiei-Esfahany Roland Klees Ramon Hanssen 《Journal of Geodesy》2018,92(1):21-32
Deformation estimates from Interferometric Synthetic Aperture Radar (InSAR) are relative: they form a ‘free’ network referred to an arbitrary datum, e.g. by assuming a reference point in the image to be stable. However, some applications require ‘absolute’ InSAR estimates, i.e. expressed in a well-defined terrestrial reference frame, e.g. to compare InSAR results with those of other techniques. We propose a methodology based on collocated InSAR and Global Navigation Satellite System (GNSS) measurements, achieved by rigidly attaching phase-stable millimetre-precision compact active radar transponders to GNSS antennas. We demonstrate this concept through a simulated example and practical case studies in the Netherlands. 相似文献
432.
Su Kong Ngien Norhan A. Rahman Roland W. Lewis Kamarudin Ahmad 《国际地质力学数值与分析法杂志》2012,36(10):1330-1349
A numerical model describing the flow of multiphase, immiscible fluids in a deformable, double‐porosity featured soil has been developed. The model is focused on the modelling of the secondary porosity features in soil, which is more relevant to groundwater contamination problems. The non‐linear saturation and relative permeabilities were expressed as functions of the capillary pressures. The governing partial differential equations in terms of soil displacement and fluid pressures were solved numerically. Galerkin's weighted‐residual finite element method was employed to obtain the spatial discretization whereas temporal discretization was achieved using a fully implicit scheme. The model was verified against established, peer‐reviewed works, and the assumption that the immiscible fluids (non‐aqueous phase liquids) will flow preferentially through the secondary porosity features in soil was validated. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
433.
434.
Katrin Stephan Ralf Jaumann Roland Wagner Dale P. Cruikshank Thomas Roatsch Robert H. Brown Bonnie J. Buratti Tom B. McCord Kevin H. Baines 《Icarus》2010,206(2):631-652
We present a detailed analysis of the variations in spectral properties across the surface of Saturn’s satellite Dione using Cassini/VIMS data and their relationships to geological and/or morphological characteristics as seen in the Cassini/ISS images. This analysis focuses on a local region on Dione’s anti-saturnian hemisphere that was observed by VIMS with high spatial resolution during orbit 16 in October 2005. The results are incorporated into a global context provided by VIMS data acquired within Cassini’s first 50 orbits. Our results show that Dione’s surface is dominated by at least one global process. Bombardment by magnetospheric particles is consistent with the concentration of dark material and enhanced CO2 absorption on the trailing hemisphere of Dione independent of the geology. Local regions within this terrain indicate a special kind of resurfacing that probably is related to large-scale impact process. In contrast, the enhanced ice signature on the leading side is associated with the extended ejecta of the fresh impact crater Creusa (∼49°N/76°W). Although no geologically active regions could be identified, Dione’s tectonized regions observed with high spatial resolution partly show some clean H2O ice implying that tectonic processes could have continued into more recent times. 相似文献
435.
Laboratory experiments were conducted to simulate chalcopyrite oxidation under anaerobic and aerobic conditions in the absence or presence of the bacterium Acidithiobacillus ferrooxidans. Experiments were carried out with 3 different oxygen isotope values of water (δ18OH2O) so that approach to equilibrium or steady-state isotope fractionation for different starting conditions could be evaluated. The contribution of dissolved O2 and water-derived oxygen to dissolved sulfate formed by chalcopyrite oxidation was unambiguously resolved during the aerobic experiments. Aerobic oxidation of chalcopyrite showed 93 ± 1% incorporation of water oxygen into the resulting sulfate during the biological experiments. Anaerobic experiments showed similar percentages of water oxygen incorporation into sulfate, but were more variable. The experiments also allowed determination of sulfate–water oxygen isotope fractionation, ε18OSO4–H2O, of ~ 3.8‰ for the anaerobic experiments. Aerobic oxidation produced apparent εSO4–H2O values (6.4‰) higher than the anaerobic experiments, possibly due to additional incorporation of dissolved O2 into sulfate. δ34SSO4 values are ~ 4‰ lower than the parent sulfide mineral during anaerobic oxidation of chalcopyrite, with no significant difference between abiotic and biological processes. For the aerobic experiments, a small depletion in δ34SSO4 of ~? 1.5 ± 0.2‰ was observed for the biological experiments. Fewer solids precipitated during oxidation under aerobic conditions than under anaerobic conditions, which may account for the observed differences in sulfur isotope fractionation under these contrasting conditions. 相似文献
436.
Damien Daval Roland Hellmann Delphine Tisserand François Guyot 《Geochimica et cosmochimica acta》2010,74(9):2615-5525
Measurements of the dissolution rate of diopside (r) were carried out as a function of the Gibbs free energy of the dissolution reaction (ΔGr) in a continuously stirred flow-through reactor at 90 °C and pH90 °C = 5.05. The overall relation between r and ΔGr was determined over a free energy range of −130.9 < ΔGr < −47.0 kJ mo1−1. The data define a highly non-linear, sigmoidal relation between r and ΔGr. At far-from-equilibrium conditions (ΔGr ? −76.2 kJ mo1−1), a rate plateau is observed. In this free energy range, the rates of dissolution are constant, independent of [Ca], [Mg] and [Si] concentrations, and independent of ΔGr. A sharp decrease of the dissolution rate (∼1 order of magnitude) occurs in the transition ΔGr region defined by −76.2 < ΔGr ? −61.5 kJ mo1−1. Dissolution closer to equilibrium (ΔGr > −61.5 kJ mo1−1) is characterised by a much weaker inverse dependence of the rates on ΔGr. Modeling the experimental r-ΔGr data with a simple classical transition state theory (TST) law as implemented in most available geochemical codes is found inappropriate. An evaluation of the consequences of the use of geochemical codes where the r-ΔGr relation is based on basic TST was carried out and applied to carbonation reactions of diopside, which, among other reactions with Ca- and Mg-bearing minerals, are considered as a promising process for the solid state sequestration of CO2 over long time spans. In order to take into account the actual experimental r-ΔGr relation in the geochemical code that we used, a new module has been developed. It reveals a dramatic overestimation of the carbonation rate when using a TST-based geochemical code. This points out that simulations of water-rock-CO2 interactions performed with classical geochemical codes should be evaluated with great caution. 相似文献
437.
Anne-Marie Weijmans Michele Cappellari Roland Bacon P. T. de Zeeuw Eric Emsellem Jesús Falcón-Barroso Harald Kuntschner Richard M. McDermid Remco C. E. van den Bosch Glenn van de Ven † 《Monthly notices of the Royal Astronomical Society》2009,398(2):561-574
We use the integral-field spectrograph SAURON to measure the stellar line-of-sight velocity distribution and absorption line strengths out to four effective radii ( R e ) in the early-type galaxies NGC 3379 and 821. With our newly developed observing technique, we can now probe these faint regions in galaxies that were previously not accessible with traditional long-slit spectroscopy. We make optimal use of the large field-of-view and high throughput of the spectrograph: by adding the signal of all ∼1400 lenslets into one spectrum, we obtain sufficient signal-to-noise in a few hours of observing time to reliably measure the absorption line kinematics and line strengths out to large radius.
We find that the line strength gradients previously observed within 1 Re remain constant out to at least 4 R e , which puts constraints on the merger histories of these galaxies. The stellar halo populations are old and metal poor. By constructing orbit-based Schwarzschild dynamical models, we find that dark matter is necessary to explain the observed kinematics in NGC 3379 and 821, with 30–50 per cent of the total matter being dark within 4 R e . The radial anisotropy in our best-fitting halo models is less than in our models without halo, due to differences in orbital structure. The halo also has an effect on the Mg b – V esc relation: its slope is steeper when a dark matter halo is added to the model. 相似文献
We find that the line strength gradients previously observed within 1 R
438.
Roland M. Avakian Edward V. Chubarian Babken V. Khachatrian Armen V. Sarkissian 《Astrophysics and Space Science》1980,68(2):347-353
The problem of the form of the flat metric in the Rosen bimetric theory is examined in the following work.It is shown, on concrete examples, how necessary it is to write down the flat metric and solve the problem of finding the gravitational field in arbitrary non-inertial frame. It is shown also how to separate the pure gravitational effects from those connected with non-inertiality of the frame by way of comparing both metrics. 相似文献
439.
The vertical distribution of dissolved aluminium in the Mediterranean Sea offshore of Corsica has been followed during a period of high biological activity (April–September). In May and August, the concentration of dissolved aluminium is at a relatively low (1.5 μg Al1?1) and rather constant value in the surface waters, while exhibiting minimum values of about 0.5 and 0.8 μg Al1?1 in April and September. It increases under the seasonal thermocline to a depth of 150–500 m. The bottom waters are characterized by a constant and relatively high value of 4 μg Al1?1.The observed concentrations of dissolved aluminium are not compatible with a precipitation-dissolution mechanism of clay minerals.The general distribution pattern and the seasonal changes of dissolved aluminium exhibit strong analogies with those of dissolved silica and nitrogen, suggesting a pre-dominant role of biological activity. It is not possible at this stage to attribute the aluminium uptake in the photic zone solely to the activity of diatoms, as suggested earlier. 相似文献
440.