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Weighted sum method for calculating ground force: an evaluation by using a portable vibrator system 总被引：1，自引：0，他引：1
Using a lightweight portable vibrator, we have evaluated the accuracy of the 'weighted sum' method for calculating ground force. Experiments in which the vibrator was suspended elastically have shown that, contrary to expectations based on standard theory, the amplitude of the weighted sum ground force was significantly above zero at high frequencies (> 500 Hz). Complementary investigations with load cells confirmed these results. If not accounted for, these deviations may introduce significant 'vibroseis-correlation noise' in processed records. Furthermore, we have demonstrated that ground force and base-plate velocity can be used to estimate the radiation impedance, which describes the interaction of (vibratory) sources with the ground. Using the mechanical characteristics of the system (i.e. maximum displacement, maximum velocity and maximum acceleration of the base-plate) and the radiation impedance, the behaviour of the portable vibrator on typical Dutch soil types was evaluated. We found that for the same sweep, more high-frequency energy could be generated on hard grounds (e.g. concrete) characterized by a higher radiation impedance than on softer grounds (e.g. clay or sand). Knowledge of this behaviour may provide important information for use in data interpretation. 相似文献
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Abstract A simple variant of the salt flux calculation is used to estimate the freshwater transport of the Labrador Current. A freshwater budget is then constructed for the Labrador Sea, comparing the summed inputs of fresh water with the fresh water lost in the Labrador Current. Our results indicate that Baffin Bay and Hudson Strait are the largest contributors to the freshwater flux of the Labrador Current. It is found that there is ample freshwater transport in the very low salinity waters to meet the required input of fresh water of northerly origin to the Middle Atlantic Bight. 相似文献
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P. M. Phillips M. A. Norbury L. V. E. Koopmans I. W. A. Browne N. J. Jackson P. N. Wilkinson A. D. Biggs R. D. Blandford A. G. de Bruyn C. D. Fassnacht P. Helbig S. Mao D. R. Marlow S. T. Myers T. J. Pearson A. C. S. Readhead D. Rusin E. Xanthopoulos 《Monthly notices of the Royal Astronomical Society》2000,319(2):L7-L11
High-resolution MERLIN observations of a newly discovered four-image gravitational lens system, B0128+437, are presented. The system was found after a careful re-analysis of the entire CLASS data set. The MERLIN observations resolve four components in a characteristic quadruple-image configuration; the maximum image separation is 542 mas and the total flux density is 48 mJy at 5 GHz. A best-fitting lens model with a singular isothermal ellipsoid results in large errors in the image positions. A significantly improved fit is obtained after the addition of a shear component, suggesting that the lensing system is more complex and may consist of multiple deflectors. The integrated radio spectrum of the background source indicates that it is a gigahertz peaked spectrum source. It may therefore be possible to resolve structure within the radio images with deep VLBI observations and thus to constrain the lensing mass distribution better. 相似文献
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Lars Bilke Thomas Fischer Carolin Helbig Charlotte Krawczyk Thomas Nagel Dmitri Naumov Sebastian Paulick Karsten Rink Agnes Sachse Sophie Schelenz Marc Walther Norihiro Watanabe Björn Zehner Jennifer Ziesch Olaf Kolditz 《Environmental Earth Sciences》2014,72(10):3881-3899
Scientific visualization is an integral part of the modeling workflow, enabling researchers to understand complex or large data sets and simulation results. A high-resolution stereoscopic virtual reality (VR) environment further enhances the possibilities of visualization. Such an environment also allows collaboration in work groups including people of different backgrounds and to present results of research projects to stakeholders or the public. The requirements for the computing equipment driving the VR environment demand specialized software applications which can be run in a parallel fashion on a set of interconnected machines. Another challenge is to devise a useful data workflow from source data sets onto the display system. Therefore, we develop software applications like the OpenGeoSys Data Explorer, custom data conversion tools for established visualization packages such as ParaView and Visualization Toolkit as well as presentation and interaction techniques for 3D applications like Unity. We demonstrate our workflow by presenting visualization results for case studies from a broad range of applications. An outlook on how visualization techniques can be deeply integrated into the simulation process is given and future technical improvements such as a simplified hardware setup are outlined. 相似文献