Farside explorer: unique science from a mission to the farside of the moon   总被引：4，自引：0，他引：4  

David Mimoun  Mark A. Wieczorek  Leon Alkalai  W. Bruce Banerdt  David Baratoux  Jean-Louis Bougeret  Sylvain Bouley  Baptiste Cecconi  Heino Falcke  Joachim Flohrer  Raphael F. Garcia  Robert Grimm  Matthias Grott  Leonid Gurvits  Ralf Jaumann  Catherine L. Johnson  Martin Knapmeyer  Naoki Kobayashi  Alexander Konovalenko  David Lawrence  Mathieu Le Feuvre  Philippe Lognonné  Clive Neal  Jürgen Oberst  Nils Olsen  Huub R?ttgering  Tilman Spohn  Susanne Vennerstrom  Graham Woan  Philippe Zarka 《Experimental Astronomy》2012,33(2-3):529-585

Farside Explorer is a proposed Cosmic Vision medium-size mission to the farside of the Moon consisting of two landers and an instrumented relay satellite. The farside of the Moon is a unique scientific platform in that it is shielded from terrestrial radio-frequency interference, it recorded the primary differentiation and evolution of the Moon, it can be continuously monitored from the Earth–Moon L2 Lagrange point, and there is a complete lack of reflected solar illumination from the Earth. Farside Explorer will exploit these properties and make the first radio-astronomy measurements from the most radio-quiet region of near-Earth space, determine the internal structure and thermal evolution of the Moon, from crust to core, and quantify impact hazards in near-Earth space by the measurement of flashes generated by impact events. The Farside Explorer flight system includes two identical solar-powered landers and a science/telecommunications relay satellite to be placed in a halo orbit about the Earth–Moon L2 Lagrange point. One lander would explore the largest and oldest recognized impact basin in the Solar System— the South Pole–Aitken basin—and the other would investigate the primordial highlands crust. Radio astronomy, geophysical, and geochemical instruments would be deployed on the surface, and the relay satellite would continuously monitor the surface for impact events.  相似文献   

Silver and lead in high-altitude lake sediments: Proxies for climate changes and human activities     

Marion Garçon  Catherine Chauvel  Emmanuel Chapron  Xavier Faïn  Mingfang Lin  Sylvain Campillo  Sarah Bureau  Marc Desmet  Marie-Christine Bailly-Maître  Laurent Charlet 《Applied Geochemistry》2012

High-altitude lake sediments are often used as archives for environmental changes and their chemical and isotopic compositions provide significant constraints on natural and anthropogenic long-term changes that have occurred in their catchment area. Here, trace-element concentrations and Pb isotopes are presented for two sedimentary cores from Lake Blanc Huez in the French Alps, to trace the impact of climate changes and human activities over the Holocene. Lead and Ag contents are very high and clearly dominated by input from a Pb–Ag vein located a few meters from the lakeshore, a vein that also buffers the Pb isotopes. Mining of this vein in medieval times is recorded in the corresponding lake sediments with high Ag content coupled with high Pb/U ratio. These chemical characteristics can be used to constrain the major Holocene climate changes. Significant advances of glaciers next to the lake produced sediments with Ag and Pb concentration peaks and high Pb/U ratios due to accelerated erosion of the Pb–Ag vein, similar to the effects of the medieval mining. In contrast, reduced glacier activity led to the formation of organic-rich sediments with high U and As contents and low Pb/U ratios. More generally, the observed combination of chemical changes could be used elsewhere to decipher environmental changes over long periods of time.  相似文献   

Integrated stochastic modeling of pharmaceuticals in sewage networks     

Sylvain Coutu  Timothée Pouchon  Pierre Queloz  Nathalie Vernaz 《Stochastic Environmental Research and Risk Assessment (SERRA)》2016,30(4):1087-1097

Pharmaceuticals and particularly antibiotics can harm sensitive aquatic species. Their occurrence in urban wastewater systems is the consequence of five successive processes: (i) ingestion of the substance, (ii) accumulation in the urine, (iii) excretion, (iv) degradation in the sewer system and (v) transport to the wastewater treatment plant (WTP). These processes were included in an integrated model that can be used to assess the dynamics of pharmaceuticals at a WTP inlet. First, information on sales data, posology, pharmacokinetics and toilet flushing frequency were combined to create a source model of pharmaceuticals entering a sewer system. This production function was then coupled with a transport/degradation model to simulate concentrations of pharmaceuticals at a WTP inlet. In an example application, the full model was applied to simulate the concentration of the antibiotic ciprofloxacin on an hourly time scale. In this application, the model was calibrated and validated for a case study at a WTP in Lausanne, Switzerland. Validation of the integrated approach was successful despite the high variability evident in the model results. This modeling approach has potential use in pollution management and epidemiology related to wastewater.  相似文献   

Seasonal variability of cohesive sediment aggregation in the Bach Dang–Cam Estuary, Haiphong (Vietnam)     

Jean-Pierre Lefebvre  Sylvain Ouillon  Vu Duy Vinh  Robert Arfi  Jean-Yves Panché  Xavier Mari  Chu Van Thuoc  Jean-Pascal Torréton 《Geo-Marine Letters》2012,32(2):103-121

In the Bach Dang–Cam Estuary, northern Vietnam, mechanisms governing cohesive sediment aggregation were investigated in situ in 2008–2009. As part of the Red River delta, this estuary exhibits a marked contrast in hydrological conditions between the monsoon and dry seasons. The impact on flocculation processes was assessed by means of surveys of water discharge, suspended particulate matter concentration and floc size distributions (FSDs) conducted during a tidal cycle at three selected sites along the estuary. A method was developed for calculating the relative volume concentration for the modes of various size classes from FSDs provided by the LISST 100X (Sequoia Scientific Inc.). It was found that all FSDs comprised four modes identified as particles/flocculi, fine and coarse microflocs, and macroflocs. Under the influence of the instantaneous turbulent kinetic energy, their proportions varied but without significant modification of their median diameters. In particular, when the turbulence level corresponded to a Kolmogorov microscale of less than ∼235 μm, a major breakup of flocs resulted in the formation of particles/flocculi and fine microflocs. Fluctuations in turbulence level were governed by seasonal variations in freshwater discharge and by the tidal cycle. During the wet season, strong freshwater input induced a high turbulent energy level that tended to generate sediment transfer from the coarser size classes (macroflocs, coarse microflocs) to finer ones (particles/flocculi and fine microflocs), and to promote a transport of sediment seawards. During the dry season, the influence of tides predominated. The turbulent energy level was then only episodically sufficiently high to generate transfer of sediment between floc size classes. At low turbulent energy, modifications in the proportions of floc size classes were due to differential settling. Tidal pumping produced a net upstream transport of sediment. Associated with the settling of sediment trapped in a near-bed layer at low turbulent energy, this causes the silting up of the waterways leading to the harbour of Haiphong.  相似文献   

A two-phase numerical model for suspended-sediment transport in estuaries     

Kim Dan Nguyen  Sylvain Guillou  Julien Chauchat  Nathaly Barbry 《Advances in water resources》2009

This paper presents a full 2-D X/Z numerical model for sediment transport in open channels and estuaries using a two-phase (fluid–solid particle) approach. The physical concept and the mathematical background of the model are given and test-cases have been carried out to validate the proposed model. In order to illustrate its feasibility for a real estuary, the model has been applied to simulate the suspended-sediment transport and the formation of turbidity maximum in the Seine estuary. The numerical results show that the main characteristics of estuarine hydro-sediment dynamics in the Seine estuary are in fact reproduced by the proposed model. A qualitative agreement between the numerical results and the actual observations has been obtained and is presented in this paper.  相似文献   

On the Use of Hydrological Models and Satellite Data to Study the Water Budget of River Basins Affected by Human Activities: Examples from the Garonne Basin of France     

Eric Martin  Simon Gascoin  Youen Grusson  Clément Murgue  Mélanie Bardeau  François Anctil  Sylvain Ferrant  Romain Lardy  Patrick Le Moigne  Delphine Leenhardt  Vincent Rivalland  José-Miguel Sánchez Pérez  Sabine Sauvage  Olivier Therond 《Surveys in Geophysics》2016,37(2):223-247

Natural and anthropogenic forcing factors and their changes significantly impact water resources in many river basins around the world. Information on such changes can be derived from fine scale in situ and satellite observations, used in combination with hydrological models. The latter need to account for hydrological changes caused by human activities to correctly estimate the actual water resource. In this study, we consider the catchment area of the Garonne river (in France) to investigate the capabilities of space-based observations and up-to-date hydrological modeling in estimating water resources of a river basin modified by human activities and a changing climate. Using the ISBA–MODCOU and SWAT hydrological models, we find that the water resources of the Garonne basin display a negative climate trend since 1960. The snow component of the two models is validated using the moderate-resolution imaging spectroradiometer snow cover extent climatology. Crop sowing dates based on remote sensing studies are also considered in the validation procedure. Use of this dataset improves the simulated evapotranspiration and river discharge amounts when compared to conventional data. Finally, we investigate the benefit of using the MAELIA multi-agent model that accounts for a realistic agricultural and management scenario. Among other results, we find that changes in crop systems have significant impacts on water uptake for agriculture. This work constitutes a basis for the construction of a future modeling framework of the sociological and hydrological system of the Garonne river region.  相似文献   

Influence of Random Inclusion of Synthetic Wicks Fibers of Hair on the Behavior of Clayey Soils     

Armand Sylvain Ludovic Wouatong  Wamba Danny Love Djukem  François Ngapgue  Valentine Katte  Véronique Kamgang Kabeyene Beyala 《Geotechnical and Geological Engineering》2017,35(6):2637-2646

Several soil improvement methods are used to enhance the engineering properties of soil, among which, reinforcement by fibers is considered as an effective ground improvement method because of its cost effectiveness, and easy adaptability. The present investigation chooses synthetic wick and vinifera raphia fibers as reinforcement. The synthetic wick fiber was randomly included into the soil at four different percentages i.e. 0, 2, 4, 6% by volume of raw soil. Vinifera raphia fiber was used at one percentage (4%) as control. The main objective of this research is to focus on the strength behavior of clayey soil reinforced with randomly included synthetic wick fiber. The physical and mineralogical characterization was carried out on ten soil samples. The compression, flexion, abrasion, water absorption and capillarity tests were performed on synthetic wick reinforced specimens with various fiber contents. The results of these tests have clearly shown an improvement in the compression strength values from 1.65 to 2.84 MPa for the wicks fibers, and the flexural strength values which varied between 1.08 and 1.96 MPa. Hence, the waste of synthetic wick fibers is therefore an efficient reinforcement for compressed earth blocks, which are very significant for construction of durable and economic infrastructures.  相似文献   

Tidal sediment transport versus freshwater flood events in the Konkouré Estuary, Republic of Guinea     

Sylvain Capo  Isabelle Brenon  Aldo Sottolichio  Patrice Castaing  Patrick Le Goulven 《Journal of African Earth Sciences》2009,55(1-2):52

In comparison to their temperate counterparts, sediment processes in tropical estuaries are poorly known and especially in African ones. The hydrodynamics of such environments is controlled by a combination of multiple processes including morphology, salinity, mangrove vegetation, tidal processes, river discharge, settling and erosion of mud and by physico-chemical processes as well as sediment dynamics.The aim of this study is to understand the sediment processes in this transitional stage of the estuary when the balance between river discharges and marine processes is reversing. Studying the hydrodynamics and sediment dynamics of the Konkouré Estuary has recently been made possible thanks to new data on bathymetry, sedimentary cover, salinity, water elevations, and current velocities. The Lower Konkouré is a shallow, funnel shaped, mesotidal mangrove-fringed, tide-dominated estuary, well mixed during low river discharge and stratified during high river discharge. The Konkouré Estuary is turbid despite the small amount of terrestrial input and its residual velocity at the mouth during low river discharges, landwards for two of the three branches, suggests a landward migration by tidal pumping of the suspended particulate matter. A Turbidity Maximum Zone (TMZ) is identified for typical states of the estuary with regard to fluvial and tidal components. Suspended sediment transport during a transitional stage between the rainy and dry seasons is known thanks to current velocity and Suspended Sediment Concentration (SSC) measurements taken in November 2003. The Richardson layered number calculation assesses that turbulence is the major mixing process in the water column, at least during the flood and ebb stages, whereas stratification occurs during the slack water periods. Tidal currents generate bottom erosion, and turbulence mixes the suspended sediment throughout the water column. As a result, a net sediment input is calculated from the western Konkouré outlet for two consecutive tidal cycles. Despite the net water export, almost 300 tons per tide reach the estuary through this outlet, for a moderate river flow.  相似文献   

Computation of GPS P1–P2 Differential Code Biases with JASON-2     

Gilles Wautelet  Sylvain Loyer  Flavien Mercier  Félix Perosanz 《GPS Solutions》2017,21(4):1619-1631

GPS Differential Code Biases (DCBs) computation is usually based on ground networks of permanent stations. The drawback of the classical methods is the need for the ionospheric delay so that any error in this quantity will map into the solution. Nowadays, many low-orbiting satellites are equipped with GPS receivers which are initially used for precise orbitography. Considering spacecrafts at an altitude above the ionosphere, the ionized contribution comes from the plasmasphere, which is less variable in time and space. Based on GPS data collected onboard JASON-2 spacecraft, we present a methodology which computes in the same adjustment the satellite and receiver DCBs in addition to the plasmaspheric vertical total electron content (VTEC) above the satellite, the average satellite bias being set to zero. Results show that GPS satellite DCB solutions are very close to those of the IGS analysis centers using ground measurements. However, the receiver DCB and VTEC are closely correlated, and their value remains sensitive to the choice of the plasmaspheric parametrization.  相似文献   

Improving runoff prediction using agronomical information in a cropped,loess covered catchment          下载免费PDF全文

Marie Lefrancq  Paul Van Dijk  Victor Jetten  Matthieu Schwob  Sylvain Payraudeau 《水文研究》2017,31(6):1408-1423

Predicting runoff hot spots and hot‐moments within a headwater crop‐catchment is of the utmost importance to reduce adverse effects on aquatic ecosystems by adapting land use management to control runoff. Reliable predictions of runoff patterns during a crop growing season remain challenging. This is mainly due to the large spatial and temporal variations of topsoil hydraulic properties controlled by complex interactions between weather, growing vegetation, and cropping operations. This interaction can significantly modify runoff patterns and few process‐based models can integrate this evolution of topsoil properties during a crop growing season at the catchment scale. Therefore, the purpose of this study was to better constrain the event‐based hydrological model Limburg Soil Erosion Model by incorporating temporal constraints for input topsoil properties during a crop growing season (LISEM). The results of the temporal constraint strategy (TCS) were compared with a classical event per event calibration strategy (EES) using multi‐scale runoff information (from plot to catchment). The EES and TCS approaches were applied in a loess catchment of 47 ha located 30 km northeast of Strasbourg (Alsace, France). A slight decrease of the Nash–Sutcliffe efficiency criterion on runoff discharge for TCS compared to EES was counterbalanced by a clear improvement of the spatial runoff patterns within the catchment. This study showed that limited agronomical and climatic information added during the calibration step improved the spatial runoff predictions of an event‐based model. Reliable prediction of runoff source, connectivity, and dynamics can then be derived and discussed with stakeholders to identify runoff hot spots and hot‐moments for subsequent land use and crop management modifications.  相似文献