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排序方式: 共有41条查询结果,搜索用时 250 毫秒
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2.
Stochastic delineation of wellhead protection area in fractured aquifers and parametric sensitivity study 总被引:1,自引:0,他引:1
S. Chevalier M. A. Buès J. Tournebize O. Banton 《Stochastic Environmental Research and Risk Assessment (SERRA)》2001,15(3):205-227
In many countries, the setup of protection areas around every drinking water well was instituted at a national level in order
to preserve the quality of water as well as the perennially of the resource. Wellhead protection surfaces have been defined
using capture zones showing the area influenced by a well within a certain time. A stochastic method is developed for delineating
time-related capture zones in fractured aquifers characterised by a low porosity and a high degree of fracturing. The flow
velocity within the fractures is determined statistically depending on the distribution of the fracture features and the mass
transfer solution is obtained through a particle tracking algorithm. Probabilistic capture zone curves are obtained as a function
of the travel time of particles to the well and the percentage of particles apt to be extracted up to this time. A sensitivity
study of fracture network parameters leads to the conclusion that orientations and aperture distribution of the fracture sets
are of primary importance to the wellhead protection delineation. 相似文献
3.
Influence of different GPS receiver antenna calibration models on geodetic positioning 总被引:1,自引:0,他引:1
Q. Baire C. Bruyninx J. Legrand E. Pottiaux W. Aerts P. Defraigne N. Bergeot J. M. Chevalier 《GPS Solutions》2014,18(4):529-539
To better understand how receiver antenna calibration models contribute to GPS positioning error budget, we compare station positions estimated with different calibration models: igs05.atx, igs08.atx and individual antenna calibrations. First, the impact of switching from the igs05.atx antenna calibration model to the igs08.atx antenna calibration model is investigated using the EUREF Permanent Network historical data set from 1996 until April 2011. It is confirmed that these position offsets can be effectively represented by the igs05.atx to igs08.atx latitude-dependent model. Then, we demonstrate that the position offsets resulting from the use of individual calibrations instead of type mean igs08.atx calibrations can reach up to 1 cm in the up component, while in the horizontal, the offsets generally stay below 4 mm. Finally, using six antennas individually calibrated by a robot as well as in an anechoic chamber, we observe a position agreement of 2 mm in the horizontal component and a bias of 5 mm in the up component. Larger position offsets, dependent on the antenna/radome type, are, however, found when these individual calibrations are compared to type mean calibrations of two tested antennas. 相似文献
4.
Bachoc François Durrande Nicolas Rullière Didier Chevalier Clément 《Mathematical Geosciences》2022,54(5):941-977
Mathematical Geosciences - Kriging is a widely employed technique across computer experiments, machine learning and geostatistics. An important challenge for kriging is its high costs when dealing... 相似文献
5.
F. Chevalier M. Guiraud J.-P. Garcia J.-L. Dommergues D. Quesne P. Allemand T. Dumont 《地学学报》2003,15(6):410-416
Displacement rates of normal faults deduced from stratigraphic data are often unreliable. Here we calculate the velocity of motion on a normal fault from the variations in accommodation potential on both sides of the fault within a high‐resolution time‐frame established by biostratigraphy and physical stratigraphy. Our example is the Ornon normal fault bounding the Early Jurassic Bourg‐d'Oisans Basin formed during Tethyan rifting. We show that motion on the fault was discontinuous when examined at high resolution and over a long time interval. During a first interval (Hettangian to Sinemurian Arietites bucklandi zone) a low rate of displacement (=202–423 m Myr?1) coeval with diffused extensional deformation throughout the sedimentary basin is observed. A second interval of localized deformation (Early Sinemurian Caenisites turneri zone) is characterized by higher rates of displacement on the fault (1846 m Myr?1). Our results concur with recent numerical models identifying the main stages of extensional deformation. 相似文献
6.
S. Turck-Chièze P. Lamy C. Carr P. H. Carton A. Chevalier I. Dandouras J. M. Defise S. Dewitte T. Dudok de Wit J. P. Halain S. Hasan J. F. Hochedez T. Horbury P. Levacher M. Meissonier N. Murphy P. Rochus A. Ruzmaikin W. Schmutz G. Thuillier S. Vivès 《Experimental Astronomy》2009,23(3):1017-1055
The DynaMICCS mission is designed to probe and understand the dynamics of crucial regions of the Sun that determine solar
variability, including the previously unexplored inner core, the radiative/convective zone interface layers, the photosphere/chromosphere
layers and the low corona. The mission delivers data and knowledge that no other known mission provides for understanding
space weather and space climate and for advancing stellar physics (internal dynamics) and fundamental physics (neutrino properties,
atomic physics, gravitational moments...). The science objectives are achieved using Doppler and magnetic measurements of
the solar surface, helioseismic and coronographic measurements, solar irradiance at different wavelengths and in-situ measurements
of plasma/energetic particles/magnetic fields. The DynaMICCS payload uses an original concept studied by Thalès Alenia Space
in the framework of the CNES call for formation flying missions: an external occultation of the solar light is obtained by
putting an occulter spacecraft 150 m (or more) in front of a second spacecraft. The occulter spacecraft, a LEO platform of
the mini sat class, e.g. PROTEUS, type carries the helioseismic and irradiance instruments and the formation flying technologies.
The latter spacecraft of the same type carries a visible and infrared coronagraph for a unique observation of the solar corona
and instrumentation for the study of the solar wind and imagers. This mission must guarantee long (one 11-year solar cycle)
and continuous observations (duty cycle > 94%) of signals that can be very weak (the gravity mode detection supposes the measurement
of velocity smaller than 1 mm/s). This assumes no interruption in observation and very stable thermal conditions. The preferred
orbit therefore is the L1 orbit, which fits these requirements very well and is also an attractive environment for the spacecraft
due to its low radiation and low perturbation (solar pressure) environment. This mission is secured by instrumental R and
D activities during the present and coming years. Some prototypes of different instruments are already built (GOLFNG, SDM)
and the performances will be checked before launch on the ground or in space through planned missions of CNES and PROBA ESA
missions (PICARD, LYRA, maybe ASPIICS). 相似文献
7.
8.
This paper highlights the importance of differentiating between precipitation amount and moisture availability (‘humidity’/‘aridity’) when considering proxy records of climate change. While the terms are sometimes used interchangeably, moisture availability is determined by both (i) precipitation amount and (ii) temperature, through its influence on potential evapotranspiration. As many palaeoenvironmental proxies reflect changes in this water balance rather than purely precipitation amount, it is important to distinguish between the potential relative influences of precipitation and temperature if those records are to be interpreted in terms of climate mechanisms and/or compared with model outputs. As a case study, we explore how precipitation and temperature have determined moisture availability in South Africa's summer rainfall zone over the last 45 000 years. Using quantitative reconstructions of mean annual temperature, summer rainfall amount and an aridity index, our analysis reveals strong spatiotemporal variability in the relative influences of precipitation and temperature on aridity. Temperature is shown to have exerted a considerable and even dominant influence on moisture availability, resulting in elevated humidity during the last glacial period, despite significant reductions in precipitation amount. 相似文献
9.
Quantification of both normal and right‐lateral late Quaternary activity along the Kongur Shan extensional system,Chinese Pamir
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The Kongur Shan Extensional System (KES) is a ~250 km long normal fault system that bounds the Muji–Tashkorgan basin of the Chinese Pamir. It accommodates E–W extension due to the northward indentation of the Pamir salient, and its late Miocene activity has been the focus of tectonic studies. While the KES has a main normal component, ~WNW–ESE‐striking segments have an additional right‐lateral strike‐slip component. Here, we quantify late Quaternary horizontal and vertical slip rates at three locations along the KES, where active faults cut and offset abandoned geomorphic features. We find rates of >3–4 mm a?1 (horizontal) along the western Muji fault in the north and of ~1.7 mm a?1 (vertical) and ~1 mm a?1 (horizontal) along the Kongur Shan fault in the south during the late Pleistocene. These rates are consistent with GPS and late Miocene rates, and imply that E–W extension in the Muji–Tashkorgan basin is faster in the north than in the south. 相似文献
10.
Possibilities to sequester anthropogenic CO2 in deep geological formations are being investigated worldwide, but the potential within Switzerland has not yet been evaluated.
This study presents a first-order appraisal based solely on geological criteria collated from the literature. The Swiss Molasse
Basin (SMB) and the adjacent Folded Jura are the only realms of the country where CO2 could conceivably be stored in saline aquifers. Evaluation of geological criteria at the basin-wide scale shows that the
SMB–Jura has moderate potential (score of 0.6 on a scale from 0 to 1) when compared to basins elsewhere. At the intrabasinal
scale, inspection of the stratigraphy reveals four regional candidate aquifers that are sealed by suitable caprocks: top Basement
plus basal Mesozoic sandstones, all sealed by the Anhydrite Group; Upper Muschelkalk sealed by the Gipskeuper; Hauptrogenstein
sealed by the Effinger Member, and Upper Malm plus Lower Cretaceous sealed by the Lower Freshwater Molasse. Nine geological
criteria are defined to evaluate the storage potential of these and other smaller scale candidates. A numerical scoring and
weighting scheme allows the criteria to be assessed simultaneously, permitting the storage potential to be depicted using
the 0–1 scale in contoured maps. Approximately 5,000 km2 of the central SMB exhibits potentials between 0.6 and 0.96. The Fribourg–Olten–Luzern area is the most favoured owing to
the presence of several sealed aquifers within the preferred 800–2,500 m depth interval, and to its low seismicity, low geothermal
gradient, low fault density, and long groundwater residence times. Smaller areas with good potential lie between Zürich and
St. Gallen. In contrast, western Switzerland, the Jura and the southern SMB have markedly poorer potential. Considering only
the portions of the aquifers with potential above 0.6, the theoretical, effective storage capacity of the basin is estimated
to be 2,680 million tonnes of CO2. 相似文献