Impacts du changement climatique sur l'hydrologie et la gestion des ressources en eau du bassin de la Meuse (synthèse bibliographique)

Impacts of climate change on hydrological regimes and water resources management in the Meuse catchment. A review. This review examines the consequences of climate change on the hydrology of the Meuse catchment and on various water-related socio-economic sectors. It sums up the different modeling approaches in hydrological modeling, placing emphasis on current modeling assumptions and the restrictions inherent within them. It is useful to consider land use evolution and adapted management within the context of climate change, particularly with reference to agriculture. More specifically, a broader usage of physically-based hydrological models would be useful in order to represent climate change scenarios and possible adaptation tracks at the catchment scale. These physically-based hydrological models are able to represent a wide range of phenomena occurring in the water-soil-plant continuum. They thus allow a refinement of global hydrological solutions at the catchment scale, especially during low flow periods. Moreover, such models pave the way for the analysis of scenarios aimed at creating adaptation in the use and management of soils

Influence de l'état d'ameublissement et de la rugosité du sol des parcelles agricoles sur l'exactitude de l'altitude des points de contrôle positionnés au GPS

Agricultural soil tilth and roughness impact on the exactness of ground control points elevation surveyed by GPS. Our goal in this study is to estimate through ranges of variation, the impact of agricultural parcels soil's tilth and roughness, due to cultivation techniques, on the exactness of ground control points elevation surveyed by RTK (Real Time Kinematic) GPS (Global Positioning System). So, 16 point's elevations which were located each 100 mm on a transect have been surveyed first by using a Total Station (TS), and then a RTK GPS in 2 parcels (3 transects per parcel). Cultivation techniques on those parcels were different. The parcel 1 was tilled, and the soil of parcel 2 was prepared for cereal cropping. Then, the analysis of variance has been applied on the differences of TS and RTK GPS elevations data to estimate the confidence interval of ground control points elevation due to soil tilth, whereas the times series statistical method has been applied on elevation data to estimate the confidence interval due to soil roughness. The confidence intervals of points elevation are estimated being [51 mm; 57 mm], [-4 mm; 4 mm] for parcel 1, and [97 mm; 113 mm], [-35 mm; 23 mm], for parcel 2. Results show that ground control point's elevations exactness is influenced by soil tilth and soil roughness. In conclusion, we can admit that soil tilth and soil roughness have significant impact on the exactness of ground control points located on agricultural parcels. This impact must be considered in Digital Elevation Model (DEM) errors evaluation of agricultural watershed

Report on the effectiveness of vegetative barriers to regulate simulated fluxes of runoff and sediment in open agricultural landscapes (Flanders, Belgium)

Vegetative barriers are increasingly used to reduce sediment export from cropland and thus mitigate negative off-site consequences of soil erosion. Here, we report and discuss the effectiveness of vegetative barriers implemented in Flanders (Belgium) to buffer the flows of water and sediment. The three types of vegetative barriers studied are made of straw bales, wood chips or bales of coconut- fibre. Based on three simulated runoff experiments performed in the field, we calculated the hydraulic roughness and sediment deposition ratio. Our experiments showed that the barriers made of coconut-fibre bales performed markedly better than those of straw bales or wood chips (Manning's n values of 1.355, 1.049 and 2.231 s m-1/3 and a sediment deposition ratio of 19%, 38% and 64% for barriers made of straw bales, wood chips and coconut-fibre bales, respectively, during the first experiment). These values increased during subsequent experiments demonstrating the effect of sediment accumulating inside the structures. Especially for coconut-fibre bales, this accumulation increases the risk of runoff bypassing or overtopping the barriers. The barriers mainly retained sand and, to a lesser extent, silt and clay. As vegetative barriers have to be renewed every few years because of the decomposition of organic material, barriers made of locally available materials are more sustainable as a nature-based solution to erosion. We conclude that although the vegetative barriers made of coconut-fibre bales are superior in their regulation of flows of runoff and sediment, barriers made of locally sourced materials are more sustainable. © 2021 John Wiley & Sons, Ltd

Study of Spin and Decay-Plane Correlations of W Bosons in the e+e- -> W+W- Process at LEP

Data collected at LEP at centre-of-mass energies \sqrt(s) = 189 - 209 GeV are used to study correlations of the spin of W bosons using e+e- -> W+W- -> lnqq~ events. Spin correlations are favoured by data, and found to agree with the Standard Model predictions. In addition, correlations between the W-boson decay planes are studied in e+e- -> W+W- -> lnqq~ and e+e- -> W+W- -> qq~qq~ events. Decay-plane correlations, consistent with zero and with the Standard Model predictions, are measured

Ultrarelativistic sources in nonlinear electrodynamics

The fields of rapidly moving sources are studied within nonlinear electrodynamics by boosting the fields of sources at rest. As a consequence of the ultrarelativistic limit the delta-like electromagnetic shock waves are found. The character of the field within the shock depends on the theory of nonlinear electrodynamics considered. In particular, we obtain the field of an ultrarelativistic charge in the Born-Infeld theory.Comment: 10 pages, 3 figure

Measurement of the Cross Section for Open-Beauty Production in Photon-Photon Collisions at LEP

The cross section for open-beauty production in photon-photon collisions is measured using the whole high-energy and high-luminosity data sample collected by the L3 detector at LEP. This corresponds to 627/pb of integrated luminosity for electron-positron centre-of-mass energies from 189GeV to 209GeV. Events containing b quarks are identified through their semi-leptonic decay into electrons or muons. The e+e- -> e+e-b b~X cross section is measured within our fiducial volume and then extrapolated to the full phase space. These results are found to be in significant excess with respect to Monte Carlo predictions and next-to-leading order QCD calculations

Measurement of the W+W-gamma Cross Section and Direct Limits on Anomalous Quartic Gauge Boson Couplings at LEP

The process e+e- -> W+W-gamma is analysed using the data collected with the L3 detector at LEP at a centre-of-mass energy of 188.6GeV, corresponding to an integrated luminosity of 176.8pb^-1. Based on a sample of 42 selected W+W- candidates containing an isolated hard photon, the W+W-gamma cross section, defined within phase-space cuts, is measured to be: sigma_WWgamma = 290 +/- 80 +/- 16 fb, consistent with the Standard Model expectation. Including the process e+e- -> nu nu gamma gamma, limits are derived on anomalous contributions to the Standard Model quartic vertices W+W- gamma gamma and W+W-Z gamma at 95% CL: -0.043 GeV^-2 < a_0/Lambda^2 < 0.043 GeV^-2 0.08 GeV^-2 < a_c/Lambda^2 < 0.13 GeV^-2 0.41 GeV^-2 < a_n/Lambda^2 < 0.37 GeV^-2

Production of Single W Bosons at \sqrt{s}=189 GeV and Measurement of WWgamma Gauge Couplings

Single W boson production in electron-positron collisions is studied with the L3 detector at LEP. The data sample collected at a centre-of-mass energy of \sqrt{s} = 188.7GeV corresponds to an integrated luminosity of 176.4pb^-1. Events with a single energetic lepton or two acoplanar hadronic jets are selected. Within phase-space cuts, the total cross-section is measured to be 0.53 +/- 0.12 +/- 0.03 pb, consistent with the Standard Model expectation. Including our single W boson results obtained at lower \sqrt{s}, the WWgamma gauge couplings kappa_gamma and lambda_gamma are determined to be kappa_gamma = 0.93 +/- 0.16 +/- 0.09 and lambda_gamma = -0.31 +0.68 -0.19 +/- 0.13

Search for an invisibly decaying Higgs boson in e^+e^- collisions at \sqrt{s} = 183 - 189 GeV

A search for a Higgs boson decaying into invisible particles is performed using the data collected at LEP by the L3 experiment at centre-of-mass energies of 183 GeV and 189 GeV. The integrated luminosities are respectively 55.3 pb^-1 and 176.4 pb^-1. The observed candidates are consistent with the expectations from Standard Model processes. In the hypothesis that the production cross section of this Higgs boson equals the Standard Model one and the branching ratio into invisible particles is 100%, a lower mass limit of 89.2 GeV is set at 95% confidence level

Measurement of Bose-Einstein Correlations in e+e- -> W+W- at root(s)=189GeV

We investigate Bose-Einstein correlations (BEC) in W-pair production at root(s)=189GeV using the L3 detector at LEP. We observe BEC between particles from a single W decay in good agreement with those from a light-quark Z decay sample. We investigate their possible existence between particles coming from different W's. No evidence for such inter-W BEC is found