排序方式： 共有13条查询结果，搜索用时 312 毫秒
1.
Marie Auclair Michel Lamothe France Lagroix Subir K. Banerjee 《Quaternary Geochronology》2007,2(1-4):34-38
Infrared stimulated luminescence (IRSL) properties of the Old Crow tephra and bracketing loess from the Halfway House site in Central Alaska are investigated in order to test newly developed techniques, including SAR and recently proposed fading corrections. Loess samples investigated show a standard growth of luminescence with regenerative dose while the tephra sample is less sensitive by an order of magnitude and saturates at lower dose. The growth curves obtained using multiple-aliquots regeneration (MAR) saturate at a higher value than those with the single-aliquot regeneration (SAR) protocol. Fading rate determinations for these samples are shown to be imprecise and no noticeable difference was observed between loess and tephra materials. Anomalous fading corrections using an average g value of 5% are applied to the natural test dose signal intensity using the dose rate correction (DRC) method. IRSL ages obtained for loess are in agreement with the expected age while the tephra age is lower than expected, suggesting the measured fading rate is underestimated for this material. 相似文献
2.
S. Balescu J-F. Ritz M. Lamothe M. Auclair M. Todbileg 《Quaternary Geochronology》2007,2(1-4):290-295
In an attempt to date a palaeolandslide that took place along the Baga Bogd Massif, in Mongolia, the infrared stimulated luminescence (IRSL) method has been applied to lacustrine silty sediments directly overlying the landslide mass. The IRSL age estimates obtained on alkali feldspar grains (>40 μm) and polymineral fine grains (4–11 μm) provide a minimum age for the landslide event. The IRSL ages on alkali feldspars corrected for long-term fading using the protocol of Mejdahl (1988, 1989) suggest that the palaeolandslide occurred at the beginning of the Last Interglacial. These are in good agreement with the 10Be cosmogenic dates obtained on faulted and abandoned alluvial fans in the Gobi-Altay mountains. This study demonstrates for the first time that the IRSL dating method can successfully be applied for establishing landslide chronologies. 相似文献
3.
Low-order pressure gradient schemes in sigma coordinate models: The seamount test revisited 总被引：1，自引：0，他引：1
This paper revisits the classic seamount test used in numerous previous studies to evidence the sigma errors of the pressure gradient force (PGF) and their long-term effects on circulation. Two kinds of analysis are developed. We first consider the initial PGF errors. Then, the global level of erroneous kinetic energy is computed along a 180-day simulation. The long-term circulation appears to be better correlated to the initial vorticity errors than to the initial error diagnostics.The original feature of this study is to reconsider the currently admitted idea that Density-Jacobian type PGFs perform better than the primitive sigma formulation discretized in a straightforward way (hereafter Straightforward-Primitive PGF). Errors on the discrete hydrostatic pressure are actually closely related to the way the density field is initialized. If a mass conserving method is preferred to a straightforward initialization, the rectangular integral of the Straightforward-Primitive PGF is likely to be more accurate than the trapezoidal rule usually involved in Density-Jacobian PGFs. Errors on the vorticity field of the Straightforward-Primitive PGF depend on the discretization of the hydrostatic correction term. A modified version of the Straightforward-Primitive PGF is shown to be in better agreement with the concept of bottom torque consistency. The seamount tests show that this so-called Modified-Primitive PGF performs globally better than the current low-order Density-Jacobian PGFs. 相似文献
4.
5.
6.
7.
Carlo?CauzziEmail author Yannik?Behr Thomas?Le?Guenan John?Douglas Samuel?Auclair Jochen?Woessner John?Clinton Stefan?Wiemer 《Bulletin of Earthquake Engineering》2016,14(9):2495-2512
Based on our experience in the project REAKT, we present a methodological framework to evaluate the potential benefits and costs of using earthquake early warning (EEW) and operational earthquake forecasting (OEF) for real-time mitigation of seismic risk at nuclear facilities. We focus on evaluating the reliability, significance and usefulness of the aforementioned real-time risk-mitigation tools and on the communication of real-time earthquake information to end-users. We find that EEW and OEF have significant potential for the reduction of seismic risk at nuclear plants, although much scientific research and testing is still necessary to optimise their operation for these sensitive and highly-regulated facilities. While our test bed was Switzerland, the methodology presented here is of general interest to the community of EEW researchers and end-users and its scope is significantly beyond its specific application within REAKT. 相似文献
8.
Corinne Casiot Marc Leblanc Odile Bruneel Jean-Christian Personné Kouadio Koffi Françoise Elbaz-Poulichet 《Aquatic Geochemistry》2003,9(4):273-290
The distribution of arsenic (As(III), As(V)) and iron (Fe(II), Fe(III)) species was monitored during 1 year in a borehole drilled in the Carnoulès tailings impoundment which contains As-rich pyrite. The concentrations of total As and Fe in subsurface waters exhibited strong variations over one year, which were controlled by dissolved oxygen concentrations. At high oxygen levels, extremely high As (up to 162 mM) and Fe (up to 364 mM) concentrations were reached in the borehole, with the oxidised species predominant. As and Fe concentrations decreased 10-fold under oxygen-deficient conditions, as a result of pH increase and subsequent precipitation of As(V) and Fe(III). From drill core sections, it appeared that at low dissolved oxygen levels, As(III) was primarily released into water by the oxidation of As-rich pyrite in the unsaturated zone. Subsequent As and Fe precipitation was promoted during transport to the saturated zone; this reaction resulted in As enrichments in the sediment below the water table compared to the original content in pyrite, together with the formation of As-rich (up to 35 wt% As) ferruginous material in the unsaturated zone. High amounts of As(V) were released from these secondary phases during leaching experiments with oxygenated acid sulfate-rich waters; this process is believed to contribute to As(V) enrichment in the subsurface waters of the Carnoulès tailings during periods of high dissolved oxygen level. 相似文献
9.
The adsorption of phosphorus on natural diagenetic iron (Feox) and manganese (Mnox) oxyhydroxides was studied in deep and littoral zone sediments of mesotrophic Lac Saint-Charles (46°56 N, 71°23 W), using a Teflon sheet technique for collecting diagenetically produced metal oxyhydroxides. Collected metal oxide amounts were greater at the deep-water station, relative to littoral zone stations reflecting sediment and local diagenetic differences. Two-layer surface complexation modeling on iron oxyhydroxide was consistent with the measured total P/Fe molar ratios except for the upper mixed Mn–Fe oxide layer from the littoral stations, where measured phosphorus exceeded the modeled phosphorus by more than fivefold. Soluble reactive phosphorus (SRP) exchange between oxyhydroxide samples and natural lake water in the laboratory revealed a labile phosphorus pool. Phosphorus determined on the Teflon sheets from the littoral zone stations appears to be related to a distinct non-humic organic carbon pool that readily exchanges SRP, while little exchange was observed from material collected from the deep-water station. We suggest that the enhanced SRP release from littoral zone sediments is due to an organic carbon and/or metal oxide-impoverished sediment matrix, limiting microbial oxide reduction and allowing phosphorus to be rapidly recycled at the sediment–water interface, instead of being slowly incorporated into humic material. The SRP fluxes revealed in our study, which originate from the solid phase at the sediment–water interface, would be difficult to resolve using interstitial pore-water samplers and might be a quantitatively important source of inorganic phosphorus in Shield lakes. 相似文献
10.
Francis Auclair Claude Estournel Jochem W. Floor Marine Herrmann Cyril Nguyen Patrick Marsaleix 《Ocean Modelling》2011,36(1-2):49-70
An original implementation of a non-hydrostatic, free-surface algorithm based on a pressure correction method is proposed for ocean modelling. The free surface is implemented through an explicit scheme combined with a mode-spitting method but the depth-averaged velocity and the position of the free surface are updated at each non-hydrostatic iteration. The vertical momentum equation is also integrated up to the surface enabling a natural and accurate treatment of the surface layer. The consistent specification of the numerical schemes provides balanced transfers of potential and kinetic energy. This algorithm is well-suited for implementation as a non-hydrostatic kernel on originally hydrostatic free-surface ocean models such as Symphonie (http://poc.obs-mip.fr/pages/research_topics/modelling/symphonie/symphonie.htm) for which it has originally been developed.Energy balances associated with the propagation of short surface waves and solitary waves are presented for two dedicated well-documented configurations over closed domains. The buoyancy flux, the work rate of the pressure force together with the power of the advective terms are evaluated and discussed for the generation and the propagation of these two types of waves. The dissipation rate is in particular shown to be several orders of magnitude smaller than the work rates of the hydrostatic and non-hydrostatic pressure forces confirming the necessity for the exchanges of energy to be numerically balanced. The algorithm is subsequently applied to the complex generation of non-linear solitary internal waves by surface tides over Georges Bank, in the Gulf of Maine. The generation and the propagation of the observed non-linear and non-hydrostatic features in this region are correctly reproduced. 相似文献