Turbulent kinetic energy budget in a gravel-bed channel flow     

Emmanuel Mignot  Eric Barthélemy  David Hurther 《Acta Geophysica》2008,56(3):601-613

The present experimental investigation focuses on the characteristics of near bed turbulence in a fully rough, uniform open-channel flow over a gravel-type bed. Due to bed topography small scale heterogeneity, the flow is not uniform locally in the near bed region and a double averaging methodology is applied over a length scale much larger than the gravel size. The double-averaged Turbulent Kinetic Energy (TKE) budget derived in the context of the present flow over a gravel bed differs from the TKE budget written for flow over a vegetation canopy. The non-constant shape of the roughness function measured in our gravel bed leads to an additional bed-induced production term which is null for vertical roughness elements, such as simplified vegetation elements. The experimental estimation of the terms of the TKE budget reveals that the maximum turbulent activity takes place away from the reference plane, near the roughness crests. However, within the interface sublayer the work of the bed induced velocity fluctuations against the Reynolds stress is of the same magnitude as the main turbulence production term. Consequently, the characteristics of the TKE budget have similarities with uniform flows over canopies and strongly differ from uniform flows over smooth and transitionally rough flows over sedimentlike beds.  相似文献   

From 2D to 3D Modeling of Mineral Prospectivity Using Multi-source Geoscience Datasets,Wulong Gold District,China     

Zhang  Zhiqiang  Zhang  Jiaojiao  Wang  Gongwen  Carranza  Emmanuel John M.  Pang  Zong  Wang  Hao 《Natural Resources Research》2020,29(1):345-364

Natural Resources Research - The Wulong gold district (WGD) is located at the northeastern margin of the North China Carton (NCC) on the Liaodong Peninsula, China. The results of early mineral...  相似文献   

Distributed Space Segment for High Energy Astrophysics: Similarities And specificites     

Emmanuel Hinglais 《Experimental Astronomy》2005,20(1-3):435-445

This paper analyses two height energy astrophysics missions, MAX and SIMBOL-X, which have been studied in CNES in the frame of a large formation flying study program. It is particularly interesting to notice that the scientific specifications of two different missions lead to the same engineering solutions for the whole mission aspects and then advocate for a similar space segment architecture and re-use of common elements, thus allowing potential cost reductions for a second mission.In deed, the same level of data to download and a similar signal-to-noise ratio requirements leads to the same orbit and communications system, the same level of pointing precision and distance inter satellites lead to the same formation flying Guidance Navigation and Command (GNC) architecture. At the end, the same level of mass and thermal constraints leads to the same range of platform and the same propulsion systems and finally to the same launcher.  相似文献   

Regional modelling of groundwater flow and salt and environmental tracer transport in deep aquifers in the Paris Basin     

Huai Fu Wei  Emmanuel Ledoux  Ghislain De Marsily 《Journal of Hydrology》1990,120(1-4):341-358

A hydrodynamic model which takes into account the aquitard storage effect was developed for the deep multilayered system including the Dogger aquifer and its surroundings in the Paris Basin. It provides a good explanation for a series of observations in the Dogger concerning, for instance, the hydraulic head, the salinity and the transmissivity. The calibration of the model also makes it possible to estimate some unmeasured parameters such as the aquifer and aquitard storage coefficients. Finally, the results of simulations of the transport of ⁴He and ¹⁴C strengthen the representativeness of the model. The Darcy average horizontal velocity in the Dogger, obtained with the model, is of the order of 0.33m year⁻¹.  相似文献   

Data-Driven Index Overlay and Boolean Logic Mineral Prospectivity Modeling in Greenfields Exploration     

Mahyar Yousefi  Emmanuel John M. Carranza 《Natural Resources Research》2016,25(1):3-18

Index overlay and Boolean logic are two techniques customarily applied for knowledge-driven modeling of prospectivity for mineral deposits, whereby weights of values in evidential maps and weights of every evidence map are assigned based on expert opinion. In the Boolean logic technique for mineral prospectivity modeling (MPM), threshold evidential values for creating binary maps are defined based on expert opinion as well. This practice of assigning weights based on expert opinion involves trial-and-error and introduces bias in evaluating relative importance of both evidential values and individual evidential maps. In this paper, we propose a data-driven index overlay MPM technique whereby weights of individual evidential maps are derived from data. We also propose a data-driven Boolean logic MPM technique, whereby thresholds for creating binary maps are defined based on data. For assigning weights and defining thresholds in these proposed data-driven MPM techniques, we applied a prediction-area plot from which we can estimate the predictive ability of each evidential map with respect to known mineral occurrences, and we use that predictive ability estimate to assign weights to evidential map and to select thresholds for generating binary predictor maps. To demonstrate these procedures, we applied them to an area in the Kerman province in southeast Iran as a MPM case study for porphyry-Cu deposits.  相似文献   

Assessment of wind-forcing impact on a global wind-wave model using the TOPEX altimeter     

Hui Feng  Doug Vandemark  Yves Quilfen  Bertrand Chapron  Brian Beckley 《Ocean Engineering》2006,33(11-12):1431-1461

The study presents assessment of an operational wave model (Wavewatch III), focusing upon the model sensitivity to wind-forcing products. Four wind fields are used to drive the model, including the NCEP/NCAR reanalysis and three other products that assimilate various satellite wind measurements having high spatial resolution, including the QuikSCAT scatterometer. Three wave field statistics: significant wave height, mean zero-crossing wave period, and mean square slope are compared with collocated TOPEX altimeter derivatives to gauge the relative skill of differing wind-forced model runs, as well as to demonstrate an extended use of the altimeter beyond simply supplying wave height for wave model validation and assimilation. Results suggest that model output is critically sensitive to choice of the wind field product. Higher spatial resolution in the wind fields does lead to improved agreement for the higher-order wave statistics.  相似文献   

Chondrule heritage and thermal histories from trace element and oxygen isotope analyses of chondrules and amoeboid olivine aggregates          下载免费PDF全文

Emmanuel Jacquet  Yves Marrocchi 《Meteoritics & planetary science》2017,52(12):2672-2694

We report combined oxygen isotope and mineral‐scale trace element analyses of amoeboid olivine aggregates (AOA) and chondrules in ungrouped carbonaceous chondrite, Northwest Africa 5958. The trace element geochemistry of olivine in AOA, for the first time measured by LA‐ICP‐MS, is consistent with a condensation origin, although the shallow slope of its rare earth element (REE) pattern is yet to be physically explained. Ferromagnesian silicates in type I chondrules resemble those in other carbonaceous chondrites both geochemically and isotopically, and we find a correlation between ¹⁶O enrichment and many incompatible elements in olivine. The variation in incompatible element concentrations may relate to varying amounts of olivine crystallization during a subisothermal stage of chondrule‐forming events, the duration of which may be anticorrelated with the local solid/gas ratio if this was the determinant of oxygen isotopic ratios as proposed recently. While aqueous alteration has depleted many chondrule mesostases in REE, some chondrules show recognizable subdued group II‐like patterns supporting the idea that the immediate precursors of chondrules were nebular condensates.  相似文献   

Major postglacial summer temperature changes in the central coniferous boreal forest of Quebec (Canada) inferred using chironomid assemblages          下载免费PDF全文

Lisa Bajolle  Isabelle Larocque‐Tobler  Emmanuel Gandouin  Martin Lavoie  Yves Bergeron  Adam A. Ali 《第四纪科学杂志》2018,33(4):409-420

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Assessment of Geochemical Anomaly Uncertainty Through Geostatistical Simulation and Singularity Analysis   总被引：1，自引：0，他引：1  

Liu  Yue  Cheng  Qiuming  Carranza  Emmanuel John M.  Zhou  Kefa 《Natural Resources Research》2019,28(1):199-212

Natural Resources Research - Geochemical anomalies are commonly separated into different geochemical anomaly levels based on one or more thresholds. However, this practice may cause some important...  相似文献   

An Improved Data-Driven Multiple Criteria Decision-Making Procedure for Spatial Modeling of Mineral Prospectivity: Adaption of Prediction–Area Plot and Logistic Functions     

Ghezelbash  Reza  Maghsoudi  Abbas  Carranza  Emmanuel John M. 《Natural Resources Research》2019,28(4):1299-1316

Natural Resources Research - Assigning realistic weights to targeting criteria in order to synthesize various geo-spatial datasets is one of the most important challenging tasks for mineral...  相似文献