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排序方式: 共有236条查询结果,搜索用时 15 毫秒
71.
David Besson Olivier Parize Jean-Loup Rubino Jean-Pierre Aguilar Marie-Pierre Aubry Bernard Beaudoin William A. Berggren Georges Clauzon Philippe Crumeyrolle Yann Dexcoté Nicolas Fiet Silvia Iaccarino Gonzalo Jiménez-Moreno Cécile Laporte-Galaa Jacques Michaux Katharina von Salis Jean-Pierre Suc Jean-Yves Reynaud Roland Wernli 《Comptes Rendus Geoscience》2005,337(12):1045-1054
An integrated study combining facies analysis, multiple group biostratigraphy, identification of depositional sequences and mapping has been conducted on the Miocene Molasse Basin of the external Alps (southeastern France). The filling of the basin is described as resulting from a succession of fluvial incisions subsequently filled during marine transgressions. The major incision is dated as Latest Burdigalian and the major transgression as Langhian. This revised interpretation of the Miocene physiographic evolution of the Molasse Basin implies a re-examination of previous stratigraphic correlations within the basin. To cite this article: D. Besson et al., C. R. Geoscience 337 (2005). 相似文献
72.
The weighted-residual technique, the indirect boundary element method, the truncated indirect boundary element method and the direct boundary element method can be used to analyse nonlinear soil-structure interaction in the time domain. They are illustrated and compared by using the one-dimensional dynamic problem of the spherical cavity in an infinite space. For realistic time steps, all formulations lead to accurate results, but the weighted-residual technique and the truncated indirect boundary element method are much more efficient than the direct boundary element method in the time domain. Hysteretic damping leads to noncausal behaviour, which can, however, be neglected from a practical point of view. 相似文献
73.
The various boundary-element methods, well established in the frequency domain, are developed in the time domain for a foundation embedded in a layered halfspace. They are the weighted-residual technique and the indirect boundary-element method, based on a weighted-residual equation, and the direct boundary-element method based on a reciprocity equation, both equations involving time and space. In the indirect approach, formulating the weighted-residual equation over the last time step only results in the truncated indirect boundary-element formulation which requires a reduced computational effort. In all cases, convolution integrals occur. The truncated indirect boundary-element method leads to a highly reliable algorithm, as is verified when a linear analysis in the time domain is compared to the corresponding one in the frequency domain. This boundary-element formulation, which is non-local in space and time, represents a rigorous generally applicable method taking into account a layered halfspace in a non-linear soil-structure interaction analysis. As an example, the non-linear soil-structure interaction analysis of a structure embedded in a halfspace with partial uplift of the basemat and separation of the side wall is investigated. 相似文献
74.
Iwan ROELANDTS Guy ROBAYE Panagiotis ALOUPOGIANNIS Georges WEBER Jeanne-Marie DELBROUCK-HABARU 《Geostandards and Geoanalytical Research》1987,11(1):79-80
Eighteen new Chinese standard reference samples (including stream sediments, soils and rocks) have been analysed by an automated proton induced gamma ray emission (PIGE) method for fluorine. Results of determinations are reported and are generally in good agreement with the "usable values" previously published. 相似文献
75.
Georges BLAHA 《Journal of Geodesy》1984,58(1):1-30
The geometrical approach to the least-squares, based on differential geometry with tensor structure and notations, describes
the adjustment theory in a simple and plausible manner. The development relies heavily on orthonormal space and surface vectors,
and on the extrinsic properties of surfaces linking the two kinds of vectors. In order to relate geometry to adjustments,
the geometrical concepts are extended to an n-dimensional space and u- or r-dimensional surfaces, where n is the number of
observations, u is the number of parameters in the parametric method and r is the number of conditions in the condition method,
with n=u+r. Connection is made to Hilbert spaces by demonstrating that the tensor approach to the least-squares is a classical
case of the Hilbert-space approach. 相似文献
76.
In single‐streamer acquisition, the use of acoustic transducers to constrain the receiver positions is not possible, thus implying the use of compass birds to gather information on the streamer location. The compasses are, however, sensitive to the declination of the local magnetic field of the earth, and local fluctuations not accounted for can degrade the accuracy of reconstructed positions. In order to correct these small‐scale fluctuations, we propose a simple deterministic method to calculate a spatial correction to apply to the compasses that enhances the positioning accuracy. The local compass declination is calculated after a first reconstruction on the whole survey area. This method was applied with success to navigation data from a 3D survey offshore Japan, and the positioning accuracy was improved to the level of the DGPS accuracy. 相似文献
77.
Variability of atmospheric 14C content often complicates radiocarbon-based chronologies; however, specific features such as periods of constant 14C age or steep changes in radiocarbon ages can be useful stratigraphic markers. The Younger Dryas event in the Northern Hemisphere is one of those periods, showing conspicuous 14C wiggles. Although the origin of those variations is not fully understood, we can make practical use of them and determine: (i) whether the Younger Dryas was global in extent; if so, (ii) were the initial cooling and the final warming synchronous worldwide; and (iii) what are the implications of these similarities/differences? Here we report high-resolution AMS 14C chronologies from the mid-latitudes of South America that pinpoint a cool episode between 11,400 and 10,20014C yr B.P. The onset of the final cool episode of the Late Glacial in the southern mid-latitudes, i.e., the Huelmo/Mascardi Cold Reversal, preceded the onset of the Younger Dryas cold event by ∼550 calendar years. Both events ended during a radiocarbon-age plateau at ∼10,20014C yr B.P. Thus, the Huelmo/Mascardi Cold Reversal encompasses the Younger Dryas, as well as a couple of short-term cool/warm oscillations that immediately preceded its onset in the North Atlantic region. 相似文献
78.
Anne Le Friant Georges Boudon Jean-Christophe Komorowski Christine Deplus 《Comptes Rendus Geoscience》2002,334(4):235-243
Results from recent fieldwork and the Aguadomar marine survey in the Lesser Antilles clearly indicate that the volcanic field of southern Dominica has experienced three major edifice collapse events. This led to formation of the most voluminous debris avalanches known in the Caribbean Arc. Submarine hummocky morphology with plurikilometric megablocks is characteristic of debris avalanche deposits. We propose that steep slopes on the western Caribbean side of the island and intense hydrothermal alteration lead to recurrent large-scale edifice collapses. Therefore islands in the Lesser Antilles face a non-negligible risk from generation of tsunamis associated with potential future edifice collapse. To cite this article: A. Le Friant et al., C. R. Geoscience 334 (2002) 235–243. 相似文献
79.